So, firstly we are talking about first century Christians, pre 2nd/3rd Jewish revolt. The Jewish authorities still had wide religious and political power in this era.

Jesus was the opposite of the generally conceived notion of the Messiah as a Maccebean style military leader. He died, there was a distinct lack of military conquest, and his (frankly quite limited) preaching to gentiles and Samaritans didn't help

Petrene/Jamesite and the Jewish section of the Johannine community were banned from synagogue, and Paul notes that Jewish authorities openly hunted and prosecuted early Christian groups. And these were the Pharisees, a middle and lower class fundamentalist movement that became modern Judaism.

The rich, the Saducees were even more hostile, viewing them as a threat to the fragile balance of power with Rome, and having major theological differences (priestly Judaism generally denied the existence of judgement and was ambivalent to hostile about the existence of the afterlife)

The evangelical character of early Christians didn't help, it was the equivalent of a bunch of Mormons showing up at your high Anglican mass and claiming no really their were Jews in America and this is the true promised land. They were Annoying

Compared to the mostly insular Essenes and the politically powerful Zealots, the Christians were easy targets to show the Romans that Jewish authorities had it all under control.

That said, the idea all the apostles died as martyrs is laughable. Pre Nero persecutions were largely restrained and generally politically motivated.