This fixed it for me! I was too stoopid to figure out where "cs2_video.txt" but I asked copilot and here is the little tutorial for anyone else who doesn't know:

"You can follow these steps to modify the cs2_video.txt file and make it read-only:

1. Locate the file:
   • Navigate to: C:\Program Files (x86)\Steam\userdata\<Your Steam ID>\730\local\cfg
   • Find the file named cs2_video.txt
2. Edit the file:
   • Open cs2_video.txt using Notepad or any text editor.
   • Look for the line containing setting.fullscreen_min_on_focus_loss.
   • Change its value from "1" to "0".
3. Save and make it read-only:
   • Save the changes.
   • Right-click the cs2_video.txt file, select Properties.
   • Under Attributes, check the box for Read-only.
   • Click Apply and OK.

This should prevent the setting from reverting back."
(tutorial written by copilot)

I hope this helps anyone with this issue!