Interesting, a mirror image of a few people I know who were raised catholic but at some point, adopted judaism as their faith. IMO God being
One, Eternal and Indivisible is an attraction of both judaism and islam over the god-split-in-three, for someone god-oriented.
The character of Jesus in the gospels says nothing that any pious, real-life rabbi wouldn't say, now or then: blessed are the poor, the peacemakers, those who love God and whoever treats their neighbour as kindly and lovingly as they wish for themselves. Rabbi Hillel the Elder (one of several candidates for 'the real jesus') famously quipped to someone who asked him what jews believe, "That which is hateful to you, do not do to your neighbour. That is the whole Torah; the rest is commentary; go and learn."
So all 'Jesus' said was normal Jewish stuff. What that got turned into (and how) as
kabbes says, is far more important and interesting.
As far as I can tell, it wasn't the choice of God that made the original jews' beliefs different, it was that they were the first people (that we know of) to make their God "One", all-encompassing, eternal and indivisible. Rather than a human-type creature with other companions, a husband or wife, children etc. Not a pantheon or even a pair, but One. This was novel, at the time, and in a world of "many gods" must have possessed extraordinary power in the mind of a believer.
You know God was invented before Jesus or any of the Saints, right? The ethical and lifestyle rules of the Torah were rules 'jesus' will have lived by, and preached?