Three points, in response to your question.

Firstly, Roman attitudes and engagement with the Jews were more varied by far. Certainly, on the whole, Romans exhibited quite a degree of tolerance towards the Jewish religion, but they also had a lot of trouble with Jews. The first Jewish-Roman War, and the Bar Kokhba revolt, are good examples. The fusion of religious and political interests in Judea made them a fairly unstable region of the Empire and besides these revolts, even during periods of relative peace there were numerous incidents (as per Josephus).

Secondly, then, the Jews had two things going for them that the Christians did not. The first of which was that Jewish monotheism was tied to an ethnos and a locale. Romans had encountered plenty of different ethnic nations with their own local religious cultus, and the Jews fit that pattern. They were a distinct ethnic/national group in the terms that 1st century Romans understood, and they were located in a homeland (Judea), and their religious cult was tied to a specific place, (the temple). While Romans generally were not inclined to believe Jewish claims of monotheism, they found Jewish monotheism tolerable because it was in many ways similar to other religious/ethnic groupings.

Christians, on the other hand, had a religion that was trans-ethnic and geographically unbound. This meant that they could not be treated as the Jews were, and it also tied in to the spread of Christianity. Christians were a 'tribe' but one composed of citizens and ethnicities of variegated background. This meant that they did not appear as a homogenous grouping in the eyes of the Romans.

The Second aspect that Jews had going for them was antiquity. Romans in general loved antiquity, and looked at novelty with suspicion. New things were likely trouble, probably rebellious. Christianity, once it emerged as distinct from Judaism, was a 'new' religion, whereas Jews claimed an antiquity for their nation and their beliefs that outstripped Rome itself. That was respectable, Christianity was not.

When you combine those two factors, Romans were willing to accommodate, to a degree, Jewish practices, particularly in Judea. They had little reason to accommodate Christians though. Moreover, Romans (again in general) were not super-big-fans of other 'new' Eastern religions and cults popping up in the empire, which Christianity appeared to belong among, and they considered unauthorised gatherings to be hotbeds of sedition. Christians' commitment to meeting together, to actions deemed counter-cultural or politically subversive, and their general recalcitrance, all served to make them less tolerable to Roman society than the Jews.

Again, though, Jews had an uneasy and complicated relationship with Roman power, and it was hardly smooth-sailing for them all the time either.