If I remember during a previous GPU shortage (crypto?), Nvidia (and/or TSMC?) basically knew the music would stop and didn't want to be caught with its pants down after making the significant investments necessary to increase production
Not to mention that without enough competition, you can just raise prices, which, uh (gestures at Nvidia GPU price trends...)
I believe the TSMC CEO said that in a recent interview. They're aware that their now biggest customer Nvidia has a less broad product portfolio than Apple and the high volumes they buy propably won't last. It's too much of a risk to plan more Fabs based on that.
Somewhat ironically the AI boom means Nvidia would've easily made their money back on that investment though and probably even more thoroughly owned the GPGPU space.
But as it is it's not like they made any bad decisions either.
Similar thing happened with mask manufacturers during COVID.
They didn't spin up additional mask production b/c they knew the pandemic would eventually pass. They learned this lesson from SARS.
Not maxing out production during spikes (or seasonality) in demand is a key tenet of being a "rational economic actor".