Just read this, which nicely complements my observation that there must be a plot afoot to get him the hell offstage:
Keep in mind that the entire reason that Schumer and Pelosi were invited to this meeting is because Trump needs their help to keep the government open. He cannot rely on only Republican votes in either the House or the Senate. He started out on the right foot by praising bipartisan cooperation on criminal justice reform and the Farm Bill, but then everything quickly fell apart because he decided to repeat lies in front of an audience that was simply not going to countenance his mendacity.
So, not only did Trump ruin any chance he had at getting anywhere in the negotiations, but he also completely lost the battle over who would be blamed if the negotiations broke down. And, in the process, he gave another example to Senate Republicans of why they do not want him in the White House one day longer than is necessary.