It seems most of them were generated on two specific days, so I guess it was one specific thing that went wrong and then spawned several gigs of logs.C:\Program Files (x86)\Steam\dumps\reports
Me is empty. Maybe it's only for bad players?
This knowledge was brought to me by WinDirStat by the way, which I somehow either have never used before or have completely forgotten about. It's incredibly useful to get a sorted overview of which folders on your PC take up the most space though. I also threw away several gigabytes of old save files that had piled up.
Now that I've made some room, I can continue trying to figure out which game to play...