>>511065462They don't. Trump is just bullying them very effectively and they are folding. The biggest part of this is actually the libel lawsuit and the impending sale of the network. The execs need to clean up the problem in order for the sale to go through, and that's why Colbert is getting shut down.
You might think that if he goes, then the other networks would gain viewership and so do better, but the reality is that they are all losing money, so if they no longer need to compete, they will just exit the talk show business and save money.
In fact, one could make the case that the driving factor is the lack of surreptitious government funding and other government support, the absence of which has left the networks vulnerable.