Here's an interesting suspicion: Trump is only marginally literate, and hates reading so much he deals with even complex correspondence by talking it out and trusting that whatever is put in from of him at the conclusion is an accurate reflection of the discussion. This strategy has come into contact with one Stephen K. Bannon, and Bannon has already done well by it.
President Trump was reportedly not fully briefed on the executive order he signed that allowed his chief strategist Steve Bannon a seat at the meetings of the country’s top national security efforts. ...Trump was frustrated over the executive order and reportedly demanded to be looped in on the executive orders earlier in the drafting process. According to the Times, Trump demanded that his chief of staff Reince Priebus to come up with a fundamental approach to executive orders.
This came from the New York Times, which inexplicably buried the news deep inside a rambling story about White House messaging strategy.
... But for the moment, Mr. Bannon remains the president’s dominant adviser, despite Mr. Trump’s anger that he was not fully briefed on details of the executive order he signed giving his chief strategist a seat on the National Security Council, a greater source of frustration to the president than the fallout from the travel ban.
Which is to say that two weeks into the administration, there is already a striking instance of Bannon exercising power over Trump, implying serious questions about whether the latter has the intelligence and focus to resist being exploited by him and anyone else who can put something under his nose.
However angry Trump may be with Bannon, he's madder with everyone else for noticing how easily fooled he is, ranting on Twitter: "I call my own shots!"