Also: even towards the end 3dfx was burning through cash. I believe they thought they where a dot.con
They lost what 0.25 Billion in the last quater on sales of 120 Mill? I couldn't be bothered looking at the actual figures but its pretty accurate.
Primarily: the old CEO never had a clue he was a marketing guy and there motto was "We dont have it so you dont need it". There engineering department was the same "Yeah we'll get round to it when we think you need it". Pure arrogance nothing else. They told consumers what they did and did not need instead of letting the markets decide.
A poorely designed feature set competing for the same OEM space as the then massive ATI and the underdog nvidia. Both these companies had good cards with good feature sets at a comparable price.
I essentially blame the engineering team. Back in the Voodoo 1-5 days they never bothered segmenting engineering teams till the end. Essentially the company moved engineering teams when a product was complete not running teams parallel so as to cut development time (something Nvidia has mastered and ATI is fast catching up on). Is it managements fault as well? Probably but I doubt they where the main cause. Yes the made some bad decisions with STB but remember
Wall-street thought it was a good idea. Essentially the only model anyone had to work on for a success story was ATI. Everyone else came and flopped on their face. I dont think many people predicted the force they would become.
As for me I pretty much forecasted there fate once I saw the V3 specs (I was one of those pissed off agn3d readers

).