I think it's just stuff that got automatically scheduled as I added/used software over the years.
When I created a new user, it started from a blank slate with nothing scheduled and it doesn't seem to have hurt me in the slightest. I don't think any of it is necessary. I would just delete it all. If something needs to do something, it can always ask you. (But I haven't been asked to schedule anything in the two weeks since I did this and everything is working perfectly.)
I'm not saying task scheduler is causing the problem, but it would certainly explain how the problem can be fixed for 15 hours and then *while I'm not even using the computer* reappear later. But since the scheduled tasks got deleted at the same time I created a new user, I'm not sure that just deleting the tasks would solve the problem on its own. What would have been interesting would have been to install the 20H2 update (which solved the problem for most of a day) AND delete the tasks in the task scheduler.