Business Insider reports that there was a shouting match between Trump, on one side, and Esper and Milley on the other. Trump demanded 10,000 US troops for his own purposes (coup? protection of the bunker?) and Milley said nope.
Thought something was up.
Trump was making his Putin play. He has finally run into people willing to stand up to him.
Explains all the generals coming out against Trump. Presumably they already knew what happened.