What Communist fear
Communist regimes fear what they can not control. One of the things they fear the most is religion. The idea that there is something more powerful than them.
Communist leaders think they are the most powerful beings on earth. Their egos are so fragile that to show how strong they are they suppress religion to the point of trying to exterminate it from the face of their country.
In China, they have made their leader a “god” and have forced churches to pray to him. They have forced churches to remove images of God and His mother and replace them with pagan images of Mao and Xi. They have also replaced the 10 Commandments with sayings of Communism.
With the upcoming National Security laws forced upon Hong Kong churches may also see their persecution because Communists hate the faith. It won’t start at once but it will happen after they have no more visible enemies to go after. After all, Christianity is a western “imperialist” religion that is not compatible with Communism.
No matter how they try to suppress the faithful the faith will always come back. History has shown this to be true. And no matter what they think of themselves the Communist leaders and their enforcers, will one day die and be forced to see the truth. For on that day they will be judged by God Himself.