I can't delete the topic, so I'll just say, I got it working. I think the problem was it was still syncing when I shut it down because it was taking a long time to sync, dozens of minutes. And I would do things like restart Steam or the computer because everything was running so slolyl.

0.001 2025-09-18 16:45:24; Factorio 2.0.66 (build 83840, win64, steam, space-age)
0.002 Operating system: Windows 11 (build 26100)
0.000 Initializing Steam API.
0.002 Program arguments: "C:\Program Files (x86)\Steam\steamapps\common\Factorio\bin\x64\Factorio.exe"
0.002 Config path: C:/Users ...

This behavior continues even if I disable cloud saves in Steam. The game is unplayable until this issue is resolved. Searching for this issue reveals people saying the game should save to the cloud when shut down and restore it when restarted. It is restoring it when it is shut down! Nothing is ...

I can't delete my savefiles, they keep piling up and now my steam cloud is full. If I delete them from the load menu they reappear when I reload the game. Same thing if I use file manager.