I’ve always understood that they where priests of the Maccabe tradition, versus, the Herodian appointed priests, so ‘ousted priests’ would fit.
In addition, Philo Judeaeus is named as a minor second source for the existence of the sect. Philo apparently dates from 25 BC. That places him as Christ's contemporary. While he wrote little about them, it would seem the name was a familiar one at the time (in Greek, Essenos).
Exactly how this author comes to suggest they never existed is a question in itself. There may be little evidence of their existence, but that isn't confirmation of their later invention.
Born about 25 B.C.. His family, of a sacerdotal line, was one of the most powerful of the populous Jewish colony of Alexandria. His brother Alexander Lysimachus was steward to Anthony's second daughter, and married one of his sons to the daughter of Herod Agrippa, whom he had put under financial obligations. Alexander's son, Tiberius Alexander, apostatized and became procurator of Judea and Prefect of Egypt.
It would seem to me that if Philo wrote about the Essenes, albeit minor references,some weight should be given to it...
XII. (75) Moreover Palestine and Syria too are not barren of exemplary wisdom and virtue, which countries no slight portion of that most populous nation of the Jews inhabits. There is a portion of those people called Essenes, in number something more than four thousand in my opinion, who derive their name from their piety, though not according to any accurate form of the Grecian dialect, because they are above all men devoted to the service of God, not sacrificing living animals, but studying rather to preserve their own minds in a state of holiness and purity. (76) These men, in the first place, live in villages, avoiding all cities on account of the habitual lawlessness of those who inhabit them, well knowing that such a moral disease is contracted from associations with wicked men, just as a real disease might be from an impure atmosphere, and that this would stamp an incurable evil on their souls. Of these men, some cultivating the earth, and others devoting themselves to those arts which are the result of peace, benefit both themselves and all those who come in contact with them, not storing up treasures of silver and of gold, nor acquiring vast sections of the earth out of a desire for ample revenues, but providing all things which are requisite for the natural purposes of life; (77) for they alone of almost all men having been originally poor and destitute, and that too rather from their own habits and ways of life than from any real deficiency of good fortune, are nevertheless accounted very rich, judging contentment and frugality to be great abundance, as in truth they are. (78) Among those men you will find no makers of arrows, or javelins, or swords, or helmets, or breastplates, or shields; no makers of arms or of military engines; no one, in short, attending to any employment whatever connected with war, or even to any of those occupations even in peace which are easily perverted to wicked purposes; for they are utterly ignorant of all traffic, and of all commercial dealings, and of all navigation, but they repudiate and keep aloof from everything which can possibly afford any inducement to covetousness; (79) and there is not a single slave among them, but they are all free, aiding one another with a reciprocal interchange of good offices; and they condemn masters, not only as unjust, inasmuch as they corrupt the very principle of equality, but likewise as impious, because they destroy the ordinances of nature, which generated them all equally, and brought them up like a mother, as if they were all legitimate brethren, not in name only, but in reality and truth. But in their view this natural relationship of all men to one another has been thrown into disorder by designing covetousness, continually wishing to surpass others in good fortune, and which has therefore engendered alienation instead of affection, and hatred instead of friendship; (80) and leaving the logical part of philosophy, as in no respect necessary for the acquisition of virtue, to the word-catchers, and the natural part, as being too sublime for human nature to master, to those who love to converse about high objects (except indeed so far as such a study takes in the contemplation of the existence of God and of the creation of the universe), they devote all their attention to the moral part of philosophy, using as instructors the laws of their country which it would have been impossible for the human mind to devise without divine inspiration. (81) Now these laws they are taught at other times, indeed, but most especially on the seventh day, for the seventh day is accounted sacred, on which they abstain from all other employments, and frequent the sacred places which are called synagogues, and there they sit according to their age in classes, the younger sitting under the elder, and listening with eager attention in becoming order. (82) Then one, indeed, takes up the holy volume and reads it, and another of the men of the greatest experience comes forward and explains what is not very intelligible, for a great many precepts are delivered in enigmatical modes of expression, and allegorically, as the old fashion was; (83) and thus the people are taught piety, and holiness, and justice, and economy, and the science of regulating the state, and the knowledge of such things as are naturally good, or bad, or indifferent, and to choose what is right and to avoid what is wrong, using a threefold variety of definitions, and rules, and criteria, namely, the love of God, and the love of virtue, and the love of mankind. (84) Accordingly, the sacred volumes present an infinite number of instances of the disposition devoted to the love of God, and of a continued and uninterrupted purity throughout the whole of life, of a careful avoidance of oaths and of falsehood, and of a strict adherence to the principle of looking on the Deity as the cause of everything which is good and of nothing which is evil. They also furnish us with many proofs of a love of virtue, such as abstinence from all covetousness of money, from ambition, from indulgence in pleasures, temperance, endurance, and also moderation, simplicity, good temper, the absence of pride, obedience to the laws, steadiness, and everything of that kind; and, lastly, they bring forward as proofs of the love of mankind, goodwill, equality beyond all power of description, and fellowship, about which it is not unreasonable to say a few words. (85) In the first place, then, there is no one who has a house so absolutely his own private property, that it does not in some sense also belong to every one: for besides that they all dwell together in companies, the house is open to all those of the same notions, who come to them from other quarters; (86) then there is one magazine among them all; their expenses are all in common; their garments belong to them all in common; their food is common, since they all eat in messes; for there is no other people among which you can find a common use of the same house, a common adoption of one mode of living, and a common use of the same table more thoroughly established in fact than among this tribe: and is not this very natural? For whatever they, after having been working during the day, receive for their wages, that they do not retain as their own, but bring it into the common stock, and give any advantage that is to be derived from it to all who desire to avail themselves of it; (87) and those who are sick are not neglected because they are unable to contribute to the common stock, inasmuch as the tribe have in their public stock a means of supplying their necessities and aiding their weakness, so that from their ample means they support them liberally and abundantly; and they cherish respect for their elders, and honour them and care for them, just as parents are honoured and cared for by their lawful children: being supported by them in all abundance both by their personal exertions, and by innumerable contrivances.
While not a lot, it implies a certain knowledge from one who was a contemporary and, as I pointed out previously, had connections to the Herod (Antipas?) administration. There is somewhat more (I downloaded and installed his entire works...) but this is the "essence of the Essenes" from his viewpoint...pun intended.