You've probably read about this already - it's a fun topic on a lot of
computer gaming websites - but Sierra On-Line, the venerable (and now
defunct) video-game publisher almost bought out Id Software back in
'91.*

This has, of course, led to a lot of what-if speculation, and I can't
help but participate. One of the big things that led to Sierra's
downfall was its lack of skill with 3D gaming. The company was expert
with pushing sprites across the screen and used it to great success in
their adventure games and - later - in their strategy titles but when
it came to fast-moving 3D, they lagged behind and their games suffered
for it. They had Dynamix, of course, and that let them create stuff
like "Earthsiege" and "Silent Thunder", but those engines didn't offer
the same performance needed by "Doom-clones". Having the brilliance of
Carmack at their fingertips may have been enough for them to navigate
those early years of 3D gaming.

Then again, it probably wouldn't have. So much about Sierra's methods
were antithetical to what Id was about. Their games were typically
story-rich experiences with excellent production values, but also
games that rarely took chances. While the company occasionally dabbled
in more mature titles, on the whole they benefited from being seen as
a family-friendly publisher. I have also read that there was also a
somewhat top-heavy bureaucracy at Sierra that liked to fiddle with
productions in individual studios.

None of these aspects seem like an environment that the likes of
Carmack or Romero would find hospitable for long. Odds are that, had
the merger taken place, the two wouldn't have stayed with Sierra for
long, and instead moved on to create a new company. So such an
acquisition likely wouldn't have benefited Sierra for long.

It also amused me to read that Sierra balked at the purchase because
of a 'mere' $100,000; values like that are rounding errors in modern
video-game publishing, but it reminds us that - as big as Sierra was
in the '90s (and back then, Sierra was huge; it was the Electronic
Arts of its era) - it still was relatively small fry compared to the
'real' corporations of its day.

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* https://www.ign.com/articles/id-software-sierra-online-gdc-2022