He wants debates because the race is close and Biden looks and sounds very old and "out of it". If he was way ahead of Biden or if Biden looked and sounded better, he wouldn't bother.
To be honest, I barely remember their 2020 debates. I think I chose to erase them from my memories.
Yes, this makes sense if they think it's a toss up by default or they are starting down. Doesn't make sense* if they believe the Republican version of 2008 polling, would be best to lie low in that case.
*It's clear Trump simply enjoys putting on a show even when it's not necessarily optimal to do so. He might demand debates for personal reasons even if his internal polling was 60% Trump/35% Biden in the NPV hahaha
