3DFX and Nvidia ultimately put them out of business.
AFAICT, SGI was a textbook Innovator’s Dilemma case with an expensive enterprise product that’s hard to give up in the face of cheap, low-margin competition.
They built an incredible Windows NT system (for the time) but couldn’t keep up with the 6 month release cycle their competitors were on.
SGI was an incredible place to work while it lasted.
I remember at the time seeing some folks blown away that they could do SGI like stuff on a PC with a $199 add on card. It wasn't identical but it was close enough and you didn't have to switch to out of the Windows ecosystem. That kind of scaling and software inertia is just too hard to compete against.
What stopped SGI from offering such $199 add-on cards, but with their name on it?