Why would Gale be the one outlier? Because he's not. Gale is, like the other companions, a victim. Or at least I think that was certainly the intention of the game narrative (and it is arguable how well it was depicted, but that I see no other explanation why Gale would be the only one who isn't).
The reasoning I most often read in regards to this seems to be that Gale *should* have been content with what he had. It sounds very much in the vein of "he was at the top of his career, had the hot girlfriend, why wasn't he satisfied?" There seems to be very little empathy for this kind of situation. I am also very surprised how little empathy there seems to be for the year he spent locked up in his tower - many of us quite recently had a year locked away in our own "towers" as well, depending on the pandemic rules of the country you live in, and for a lot of people this was a horrible experience.
