Answer: They feared rebellion.
Step-by-step explanation:
The spread of Christianity in ancient Rome was a mass phenomenon. The new religion brought the poor together the most. In such circumstances, the Roman emperors feared for their rule. They considered Christians to be a direct threat and were therefore persecuted and killed.
Also, the Roman authorities characterized Christianity as blasphemy. The Roman governor of Judea, Pontius Pilate, therefore condemned Jesus to death.