For one, people in most government positions serve at the pleasure of the electorate and the president. Its not about whether hes done anything he could be convicted for criminally (though he has). It also about whether or not he is wanted out by the people at large.
For two, the guy literally admitted in his election response video that his goal is to continue the extrajudicial murder of people trafficking drugs, which should have nothing to do with the military. He has admitted to, and admitted he plans to continue, committing undeniable war crimes. There is no question “if” he is guilty…