After opening resmon, even if you close it, it will always start with the program.
It is uncloseable until you get into game and type toggle resmon again, which will reopen it. Then you will be able to press the x button
I noticed when editing the video that it does actually close on my taskbar before I type toggle resmon again, but still, not closeable until you get in game.
EDIT: Cool, the video exported incorrectly, great video editor microsoft… Still, the issue can be seen in the beginning when I launch the program