And you can call this a 'glitch' all you want, but I'd say it's far more than that. Nvidia was so very dominant in market share, how many times did we hear you shout about how Nvidia sells two part for every single AMD part (before you disappeared while Nvidia had absolutely nothing to show, now they have one good part so we're lucky enough to have you back)? From this two to one advantage they let their competitor outsell them. They had delay after delay and when the parts launched they failed to impress. Where are their lower end DX11 parts? This is one hell of a glitch.
If you go back further in history, you'll see that such 'glitches' occur, and markets can shift quickly.
Most obvious example is 3dfx. Completely dominated the 3d accelerator market. Then they had one 'glitch', and before you knew it, they were gone. From that point onwards, nVidia was the dominant force in the market.
But a few years later, nVidia had a 'glitch' with delivering DX9 hardware. Not only did ATi beat them to market by a few months, but ATi's chips were also considerably more powerful.
nVidia lost a lot of marketshare to ATi during the GeForce FX era. They slowly recovered with the 6000-series and then the 7000-series. Both were good products, arguably on par with ATi's offerings... but that's not enough.
nVidia didn't really return to dominance until the 8800 series. That's where ATi had their 'GeForce FX' moment, with a 'glitch' in their DX10 hardware. The HD2900 was too little, too late.
Like nVidia before them, ATi slowly recovered with the 3000-series and the 4000-series, but like with nVidia a few years earlier, they were good products, but not enough to regain dominance.
At this point in time it doesn't look like Fermi is such a big glitch as the GeForce FX or the Radeon HD2900 were. GF104 seems to be a nice recovery.
The GPU market is just a much faster mover than the CPU market for example.