I'm pretty sure he is good at filling his own pockets, but not through normal means.

The wall - since he is in real estate, he would earn a lot of money by choosing the constructor

Oil - sidestepping official channels and trying to put known friend in place ( Ukraine) + Big fossile companies trying to change the path forward, protecting their current investments through all means

Russia - at least one country that is obvious to try to manipulate things with bribery

Tax cuts - guess why

Stocks - he is known for trying to manipulate stocks well before he was the president

Trump name in license - since almost all the rest of his business failed, he needs to act like he is a legend ( ps. He's just a dumb guy with a life-time of manipulation experience)

Daddy - since he is not smart enough to get it from zero