We often think of the early Church as being pretty constantly persecuted by the Emperors in Rome and of that persecution as being pretty much constantly enforced for several hundred years. Actually, that’s not exactly how it happened. In the first place, most of the earliest persecutions weren’t Roman, at all. They were Jewish.
One thing almost everybody knows is that the earliest Christians were Jews. Now, not all of them liked that fact, and others, other Jews, mostly, didn’t like it either, but for the first 20 years or so, most of the several thousand converts to the Church were Jews. The Jewish Temple leadership tried to stop the movement, thinking of it as an heretical Jewish sect. There were several of these, over the years, some of which were tolerated, like the Essenes and Nazirites, and some of which were not, like the early Christians.
There were, in Jesus’ time, two primary divisions within the Jewish faith: the Pharisees and the Sadducees. We know about them from the Bible as well as from historians like Josephus. The Pharisees were legalists. That is, they wanted everybody to be extra-observant of every nuance of the Law of Moses. We might call them nit-picky. Other than that, they weren’t terribly different from the disciples of Jesus. They believed in life after death and a final judgment. They accepted the idea of Synagogue worship; that is, not just going to the Temple to make sacrifices, but instead gathering in local assemblies to read and sing and discuss the Word. Pharisees spent much of their time arguing with one another about exactly what was meant by various points of the Law. That they accepted Jesus as one of their own is clear by the fact that they often engaged him in such arguments. Later writers, especially non-Jews didn’t understand that, and so sometimes were harder on the Pharisees than was really merited. Many people think modern Judaism descends from this tradition.