All different forms of Pagan religions from the Slavs, Germanic peoples, Celts, Sarmatians, Alans etc. were effectively eradicated or their populace converted to Christianity.
Yet, Judaism still always had a constant minority following that was never fully eradicated. Why is this? Is it because of Judaism's ties to the Old Testament and Christianity? Were they viewed as "people of the book" and given some leeway in the same way Muslims would do ?
I answered a similar question here last week, if it helps.
What I'll add to it is that the fact that Judaism was the precursor (in the minds of Christians) to Christianity definitely made some impact. Jews were seen as having been superseded by Christians- Synagoga replaced by Ecclesia- and therefore should be led to the light of Christianity, but, at the same time, per Augustinian theology, they were seen as "witnesses" to Christianity, and not to be destroyed but to be scattered and weakened.