It all makes sense when you consider that Trump is finally, dimmly sensing he's in over his head. Things aren't going well, and those that have gotten him through the election aren't fairing so well in real life governance. Trump loves, craves and needs love from the public, and he's trying to figure out why his numbers are so low, even for "fake news". By all reports, Bannon got himself put onto the security council on the sly. Mattis is making his presence known as really, the only one there that knows what the fuck he's doing. I expect Mattis' presence is pretty dominatable, and Trump will latch onto him more and more for advice. Matts had no time for Bannon's bullshit, and made it his mission to get the Security Council back to what it should be - and that's exactly what's happened.