Okay that’s interesting, because you had this installed:
And this is a really old Legacy Nvidia driver, i only had nvidia legacy 470xx package installed on my system from my 2020 install, so i thought your installation must be older than mine
So did you downloaded the newest Manjaro ISO (Full) and Steam was pre-installed (official repo)?
Any additional errors? with:
systemctl --failed
journalctl -p 3 -xb
I think you better should install your games in your Home Partition or a extra Partition… I never installed and executes games from Root… possible im wrong here, but i think Root isnt the right Partition.
Maybe few points from my Linux Gamer Guide could help you, that you missed with your installation: