I've done big forensic write-ups of it in the past and mapped it to the FAA's accident chain model. It just so happened that he was using a distro with a weird forked DE (Pop!_OS) and just so happened that the version of the Steam package in the apt cache from when the install image was made was bugged in such a way that it would uninstall Xorg, and it just so happened that Pop!_OS didn't run an apt update when launching their GUI app manager.

When Linus saw "failed to install Steam" he turned the petulant child up to 11 and started bitching about how you always have to use the terminal in Linux, and instead of googling the error message to find out "do an update and try again" he found a page that told him how to sudo apt install steam. Most instructions like that tell you do to an apt update before an apt install, so I don't know if he either aggressively skimmed, deliberately ignored the update command because he's used to how painful Windows updates are, or if he found a source that didn't include it.

APT spat out a lot of stdout about all the packages it was going to remove, with a highlighted plaintext warning at the end which he failed to read or failed to heed.

Linus' bad attitude was a major contributing factor to the incident.