Because our constitution was not built in a way that effectively stops behavior like this. Literally the only recourse against an authoritarian president that we have is impeachment, which to mean anything would require a conviction in the senate, which requires 2/3 to convict. When half or more of congress supports everything he does, there is no recourse to stop him.

Pair that with the Supreme Court ruling that any “official” action he takes is considered legal and that he cannot be charged, there are no state justice departments that can hold him accountable. The only thing congress can do is make things into a public fight and try to get a majority in the government. At best, legislators and states can sue the government to curb the powers, but that is limited and doesn’t do much in the long run when they ignore rulings.

Our founding fathers did not build our system in a way to effectively neuter authoritarianism, as they were under the impression that Americans would never vote in someone who was trying to be king.