Some guesses, in declining order of probability. :)

• Vanity and spite. After all, he’s not emotionally mature.

• With some probability, rational attention-seeking to keep his supporters entertained and lobbyists (who bought and propagandized his way to power) satisfied. He has to deliver them goods. This is how he shows that he intends to deliver the goods… that he actually cannot deliver without changing the constitutional order very much. You can mark my words: lots of wind parks will be opened under the Trump administration, despite anything he does.

• Maybe he wants to test the mettle of the terrible Renewable Industries Complex - an industry very prone to organizing coups and hiring assassins. If I were him, I’d consider twice, all the people in the solar business that I know have been extremely menacing. ;P