The Beast was around during Jesus’ time. Islam was not. JFTR.
The man that will be the final Antichrist was not around then.
I know there are supposed to be traditions that say he was, but those are not anywhere in Scripture.
And as I said, what John saw is arguably something in a script he didn’t know, Arabic, so he drew it as a picture. Those symbols look like that script with the crossed swords. These do also resemble Greek letters, but they need not be Greek letters is the point.
Debates about exactly what he saw aside, what John saw with respect to the Antichrist featured in Revelation didn’t concern his own times (I can say that simply because we are still here long afterwards). The letters to the churches concerned his own times. After these Revelation transitions to a future.
Closer to John’s own times the premier expression of the spirit of antichrist — which involves active rejection and opposition to Christ and His Gospel and not just being a false religion (Hinduism, for example, is a false religion that does not profit its adherents but didn’t arise in a time or place expressly rejecting Christ as Islam later did) — would be found in developments in Judaism contemporaneous to John (and Revelation) that were bent on rejecting Christ and keeping Jews from becoming believers, a strong statement of a starting point for this would be the declaration to put those confessing Christ out of the Synagogues, but as for how that developed even all that wouldn’t be codified / written down for some centuries.
Let me be clear: Israel had received a form of religion from the Lord and so I’m not talking about some false religion that has no valid source as a starting point for it in Scripture. Instead, if I may compare to a hypothetical, imagine if a substantial party in Israel had told Moses that they weren’t going to go along with the revelation that he’d got from the Lord in the form of the Law but were going to stick with the religion that their fathers had known since Abraham? Could these not be properly called antimoses, of working in a spirit opposed to Moses as intermediary? So having a valid form of religion from your ancestors but refusing the revelation of the Law compares to having the Law but refusing the Gospel. And as Moses said, the Lord would send another like him (Moses) and whomever would not listen to that man the Lord would require it of them.
And, to belabor the point, Christ said that Moses spoke of Him ... so if not there then when? This puts Him saying that the Pharisees had set themselves in Moses seat in greater clarity ... the seat of Moses properly belonged to the one Moses spoke of and that makes the Pharisees that Christ spoke of out to be theological squatters.
(Side note: Moses spoke of another like him after him arising from Israel ... Christ never did ... so not only is Mad Mo S.O.L. as prophets go for not being out of Israel he’s also condemned for being against Christ.)