He likes killing, and he likes thinking of himself as s benefactor who is just so much smarter than everyone else that he’s the only one who sees the solution, who can rise above petty emotions and do what needs to be done. Sure he’s killing trillions, but only to save them from something worse that would have happened. Most people wouldn’t mind killing someone if there was a moral justification for it and they could get away with it. Just look at how people react to videos of someone stealing a bike: everyone in the thread is ready to literally murder that person. Because they think they have justification. Well, Thanos thinks he has a justification too. And he’s murdered millions up close - there’s no going back. In order for his mass murder to be excusable there has to be a larger purpose to it. There has to be.

He’s a knot of different psychoses mixed together. Primarily narcissism plus homicidal tendencies. He’s fully insane, if that did not come across somehow. Totally pinched off from the rest of reality, living in his own self-reinforcing loop. He’s got a lot of power and that makes him more and more immune to reality intruding on his fantasies.

Logic doesn’t come into it. Not only could he have created more resources… he didn’t even think that populations would just grow again and bring everything back to the same place. No he’s blindly playing out the track he’s on. The only way out is forward, because he can’t justify anything behind him otherwise. When the universe isn’t grateful for what he did, and his fantasy of being the benefactor falls apart, notice that he is ready to destroy the entire universe and become god, because how else can he escape the crushing blame for what he’s done.