Trump certainly hit the ground running in his first week, setting much of his platform in motion. I've never seen a President do so much in his first few days.
The only reason to doubt Trump was that most politicians say one thing on the campaign trail and do another once in office. Obama, for instance, sold himself in '08 as a guy who would "reach across the aisle" (he spent his eight years demonizing Republicans), who was biracial (and presumably not just loyal to just one side or the other), and who would have the "most transparent administration in history" (not even close).
In many ways, Obama was the opposite of what he claimed to be. (Thank you Saul Alinsky.)
But, Trump is not a career politician, so his campaign promises seem to be worth something.
At the same time, Trump's ego is such that he is incapable of admitting that he or his aren't the best at anything. Even when it was apparent that his inaugural crowd wasn't larger than Obama's, Trump had to insist that it was.
This is not atypical for Trump. It's almost cute, like something you'd expect from a little kid. And in a roundabout way, it shows he's not a sociopath. He just says what he thinks, without much of a filter -- and without subterfuge.
If Trump were a sociopath, as a couple of commenters on this blog have suggested he might be, he'd be a lot slicker about hiding that massive ego. But he's not even slick enough to be in control of his ego; it's in control of him.
But, we finally have a President who is going to pursue common sense policies that benefit Americans, and who eschews political correctness.
The outsize ego seems a small price to pay.