What i can only imagine is some sort of video player error
My guess is, your system is missing a video codec, probably a gstreamer plugin like libav (I don’t know what its called on Bazzite, something like gst-plugin-libav or gst-libav ...).
If you would start the game from console or find the steam log file you should see a error message. (I’m not at home now and rarely use steam, so I can’t look it up now).
Does Gentoo have something special that other distros do not?
Isn't there a Gentoo installer like with Arch?
Nope. That's the "something special". You do it manually with the help of a very well written handbook and learn a great deal about how an os works. IMO a great experience.
My guess is, your system is missing a video codec, probably a gstreamer plugin like libav (I don’t know what its called on Bazzite, something like gst-plugin-libav or gst-libav ...).
If you would start the game from console or find the steam log file you should see a error message. (I’m not at home now and rarely use steam, so I can’t look it up now).