Why is it that people with higher intelligence find enjoyment in difficult tasks and how do they not become exhausted from it?

One way for me to tell if someone is smart is that they tend to find things that stimulate them intellectually- reading non-fiction, doing math for fun, intense puzzles, or programing. That these things are actually ways for them to recharge. I realize when I try to do these things I become tired very quickly, I realize my escapism is watching TV and doom scrolling. I would love to train my brain to be more smart and innovative but doing tasks like that get me exhausted mentally and I'm not sure why.

Basically, how do smart people handle mentally challenging hobbies without becoming increasingly exhausted?