Which is not to say that Trump isn't being typically stupid and short-sighted about it all. Shall I predict exactly how much effort he had put into studying the TPP before scuttling it? Better not.
The thing is, he's in such a hurry to get adulation from his fans, that he ignores the long-term consequences. Dropping TPP essentially gives China a wide open field for its own East Asia Co-Prosperity Sphere. That's the big problem with Trump (among many others): he is one-dimensional in his thinking. He can only see the possible short-term loss of jobs and not the long-term consequences of turning Asia completely over to China.
Someone please alert Sen. Bernie Sanders about the great news, because he and most of his supporters didn't like the TPP at all. Turns out Bernie is ultimately on the same page like Trump on TPP. Feel the Bern, yo!