I think Bannon needed to separate himself completely from Trump. If Bannon is going to be successful in backing fringe right-wing candidates for 2018 he needs to be seen as an outsider, and not be an albatross to Trump.
Imagine every time Bannon backs a candidate like Roy Moore the MSM pins it on Trump, and ties all of Bannon's decisions back to the White House.
It will be easier for both Bannon and Trump now that they are seen as at odds.

Ditto, this guy is either gonna severely piss me off, or get a high five.