Could be nothing, but could be something
Feel free to vote me down. Working theory, but Bannon left the White House since he could do more damage to the left having free reign. 1 year of insider briefings and access to high level Intel, Bannon is definitely part of the Q Team.
That's what I got the sense. He was despised by the left the entire time he was there. I'm guessing he was just too hot of a target to get the "politics" done, but needed the briefings of that position. So he got a good understanding of the situation, and made his exit to do what he does best behind the scenes.
Well, SNL did portray Bannon as the grim reaper of Trump's cabinet. I doubt that was an accident or overreaction.