Linux

TLDR;
Doom was massively popular in it's day because it was and still is an awesome game played on ibm pc compatibles.
Popularity was basically nothing to do with ports to other os ses or hardware.
Doom is an "MS- DOS game" not a "windows game".

It had a brilliant shareware (free) version containing 1/3rd of the game - that spread like wildfire.
It had great multiplayer network deathmatch and coop modes.
It maybe gained a bit of notoriety by some morons (who probably didn't know what a BBS or shareware was) calling it to be banned as a "video Game Nasty" - but it'd have been insanely popular without that because of how many light years ahead it was the previous gen - say wolfenstein or catacomb abyss in basically every way.

It also grew a network of BBS communities who shared user created WADs with levels and mods and stuff extending the game's content and longevity - and creating a subculture of doom-obsessed tech geeks. Competitive home gamer "speedrunning" and stuff became possible at home as you could basically "record" and share a level on BBS and people could effectively validate each key-press to check for cheating.

It's true that it was ported to mac and linux and a few other OS fairly soon after release, but the vast majority of home gamers would have been on MS-DOS. Probably there were a bunch of workplace deathmatches on networks of solaris terminals or something like that - but if you had a pc at home, you were playing DOOM on MS-DOS.

Back in 1993/1994 and for years after linux was just nowhere near MS-DOS in popularity, stability, usability, compatibility etc. Debian was literally only just born the same year - but if you think Arch or GEntoo is hard to get up and running . . . that's peanuts to what a 1993 era linux user would be doing. In fact "linux programmer" is likely what you were - I don't believe there was such a thing as "linux user" until a years later - and it was still very painful and unstable.

Back then MS-DOS with it's CLI was stable, simple and fairly efficient - massively more so than the "windows GUIs" that would follow.
DOS was fairly cheap - and there were "other" ways to get it anyway - I don't think MS cared about home user piracy much - they just wanted B2B deals (and pre-installs with pc sellers).

"Windows" was just not relevant for gaming in 1993 - even in win'95 and win'98 days windows was not really an "operating system".
windows 3.x/95/98 was just a program that you could choose to run after booting into MS-DOS - and you'd only start up that mess if you wanted the GUI or some wizzywig programs like desktop publishers or something - of course Mackintosh was still the no1 choice for most pro GUI stuff.

Even when windows 1995/98 and so on came out for most gaming I'd have been booting into DOS anyway. everyone had a few DOS 6.2 boot disks lying around. Going into the naked DOS CLI meant you could access the large contiguous chunks of extended memory that games typically needed - starting windows always RAMmed you somewhere uncomfortable.

It wasn't really until 3d graphics drivers became packaged into directX that that Windows became a real thing for gaming.
From memory something like Grand Theft Auto (1) in about 1997 would have been the first game I would have actually started windows for.

Doom was basically 4 years old and pretty ancient by then. But it was still the number 1 multiplayer game in my house - since by that time we had a couple of PCs capable of Doom plus maybe a laptop or one brought over from a firends. . . . and a bloody unreliable BNC-coaxial bus network. Couldn't get enough PCs that could run quake well enough to be a fair fight.

However I could imagine a lot of people wanting to get up to four networked devices going to death match at home. SO that may well have been a driver for porting.

I didn't install it on weird devices like sony ericsson P800 or my ipod until much later - for example not until those devices were invented and cheap enough.
And all that was just a gimmick -or geeks fucking around "because they can" - the control interface of P800 touchscreen was just nowhere near the proper keyboard experience. If you can't simultaneously sidestep+sprint+turn and run backwards - you can't play doom.
DOOM on a ipod click-wheel - just fucking stupid - surprisingly slightly better than the P800 though.