Johannine baptism was already part of Jewish theology at the time. Water baptism the way John was engaging in it was for non-Hebrews who wanted to worship the God of Abraham, Isaac, and Jacob. Your average Joe Edomite needed to receive this baptism to be welcomed into the Jewish nation.
What was revolutionary about John's baptism was that he was doing it mainly for Hebrew Jews. We might have the Book of John tacked onto the Hebrew Bible after Malachi, then maybe the Book of Jesus immediately afterwards. From there there would probably be a continuation of the prophet records up until the sack of Jerusalem in 70 AD and then the defeat at Masada three or four years later, which may or may not be butterflied away if Jesus is not the Messiah. After the destruction takes place, the Diaspora would be irretrievably set into motion to its uttermost.