Originally Posted by
The Don
....because he cannot.
He can however fire Rod Rosenstein, appoint a compliant successor who will then fire Mueller. He might even be able to apply enough pressure to Rosenstein to persuade him to fore Mueller.
I'm guessing Sessions is next. Sessions replacement would take over the investigation from Rosenstein, who only has it because Sessions is recused. Then, that new AG can agree with Trump that donating to Democrats and saying mean things about Trump makes you an Enemy of the State so the investigation is "corrupt."