This was done simply to prevent McConnell and Ryan from screwing Trump - again - by eliminating their opportunity to pretend to be for America in upcoming budget and debt negotiations.
McConnell and Ryan were going to push budget and debt negotiations beyond midterms. Trump gains yuuuuge leverage by requiring republicans to show where they stand _before_ the midterms.
This will produce a few primary defeats for the GOPe.
:)
I think that is why he did it too. I think President Trump dealt with he McConnell and Ryan plan to screw the country effectively.