That's my conspiracy theory, and I'm sticking with it!
1. Preet Bharara used to work for Chuck Schumer, and Schumer recommended him to Obama for the U.S. Attorney's post in the Southern District of New York.
2. After Trump won the election, he decided to keep Bharara in that post to curry favor with Schumer, who was the incoming Senate minority leader for the Democrats.
3. After Schumer began working (publicly) to criticize and undermine Trump since the day Trump was inaugurated, Trump decided to take the olive branch he had extended to Schumer and set it on fire.
And so ... "Preet Bharara, you're fired!"