I had a similar case but I was the hookup, it started all just nice, after the sex dude started talking about past romances, I honestly don't know why people do this. I thought it was bad enough but then he started to teach me about League of Legends out of absolutely nowhere.
Just like you, I don't actually care, but I do my best to listen, but in my case it was a oner, while with you things seem to be developing a pattern, exchanging sex for emotional support, if anyone is using the other it is happening mutually.
Even though you don't particularly care for his problems, if you're at least somewhat of a nice person, you'll be interested in not help making his problems worse by taking part in his harmful behavior.
You could simply ask why he is on Grindr when he clearly has not got over his ex. Maybe he thinks this is what he needs to overcome it, or maybe he just wants the sex as he works on it somewhere else. Probably he didn't even put much thought to it.