If all she did was ask a question, then her next biggest mistake was to apologize for it. She should have doubled-down and stated that ‘it was just a question’, and that ‘we have to be able to ask questions in order to have discussions and debate’. By apologizing she admitted being guilty of something. They were never going to show her mercy.
That said, maybe she will rethink her life and priorities.
That is it in a nutshell. IF she had stuck to her guns NBC would have hesitated to fire her. As it was, her "admission" made it imperative.