AFAIK, it was more because a new PC clone/parts were cheaper than other platforms while still offering equal or superior sound/video abilities. (My family switched from Apple IIgs to PCs back then in part so I could play the latest Ultima games, but we wouldn't have been able to do it without favorable pricing.) You're conflating two separate years & shifts in computer ownership, though:
--In 1990-1991, PCs were just starting to dominate the market, and Origin Systems released Wing Commander, Wing Commander II, Ultima VI, and Worlds of Ultima, which were all developed (for the first time) on DOS PCs, with major improvements in graphics/sound as a result.
--Ultima Underworld came out in 1992 alongside Ultima VII, at the same time CD-ROMs became affordable and a bunch of games started coming out that used them to offer greater sound/graphics. Contrary to our preferences, though, the games most often credited with driving consumers to DOS (and making the PC a major gaming platform) were Myst and The 7th Guest.
I'm not sure whether we can draw parallels with support for Wing Commander & Linux today, though... Back then, consumers were switching to PCs because it was becoming increasingly difficult to find new games for their older computer systems -- unless MS really sabotages its own market with Windows 8, that dynamic won't be at work here. I do think that Kickstarter could be used to make developers more aware of the many people that are using Linux and only booting into Windows for games, however, and somebody like Chris Roberts taking notice would put out a pretty strong message in the game dev community, I would think.