The reality is no one wants to be left holding the bag if the industry collapses. It costs $8-15B to build a fab for DRAM. If we rush to increase capacity, and the demand drops N-fold, everyone who rushed in will lose their shirt.
Also, fabs are easily the most complex manufacturing on the planet. You don't want to rush stuff like that.
That's it? That's cheap for stuff these days. Especially when your market cap is lets see 2 trillion for tsmc. 5 trillion for NVIDIA. 1 trillion for micron. 1 trillion for Elon Musk. Intel might have to get a loan, "only" worth 350 billion.