What do these have to do with Christianity and Newman's “Essay”?
Read the whole passage from Newman -- though I don't think he went into corn gods as such, he does mention the idea of an incarnate god coming from India, the idea of baptism being of pagan origin, etc. etc.
A big part of the "free-thinker" movement of the 19th century ridiculed Christianity as merely another corn god myth.
Also, a number of things on your list (without tracking down Newman’s footnoted source, I can’t tell to what extent he was paraphrasing from his source or writing his own opinion) came into the Church directly from Judaism:
temple, incense, lamps, candles; holydays and seasons, processions, blessings on the fields; sacerdotal vestments, ecclesiastical chant (a direct descendant of Hebrew synagogue chant). Maybe the Jews got them from the pagans.