It's a MOV tagged as video/mp4. For me, FF recognizes only the audio part but if extracting the raw video URL I can play it with vlc.
They're the same thing. The problem is not the container, it's the H.265 encoded video which Firefox doesn't accept. It's not a good idea to throw raw cell phone video onto a website, first because it probably won't play everywhere, and second because there's embedded high-precision location data.
It's funny seeing this after the arguments in the mpv thread a few days ago[1] where over if VLC's extra bloat (and lack of features like stepping back a frame) is justified by it coping with diverse formats. This file doesn't play correctly for me in mpv[2], but does fine in VLC.
[1] https://news.ycombinator.com/item?id=41277014 [2] https://imgur.com/TeL4sfq
Using Firefox 129.0.1