If it is fake, how do they get seriously hurt?
As I said, they're like stuntmen. When you see a car crash in a movie, it's staged. But on the set, people do get hurt from time to time.
Wrestlers perform stunts in a sense. One wrestler climbs the ropes, jumps off to land on another. Even though they land in such a way as to make it look like they've crushed their opponent while in reality missing them, they still get bruised on the landing. Some have broken bones. One wrestler a few years ago died performing a "stunt."
Other stunts include tossing themselves out of the ring, lifting up an opponent and throwing him down, etc. Again, it's all rehearsed, but it still requires exertion, which can result in injury.