Buying all the RAM can't work forever. Scarcity increases prices, high prices increase supply, improves RAM R&D budgets, and forces users to find ways to economize around low RAM availability.
It doesn't need to work forever. You just need to delay your competitors long enough that you can IPO to great fanfare, and then leave retail investors holding the bag. Founders and big investors get to cash out, everyone else gets screwed.
I doubt that works today. Look at SpaceX the fanfare lasted 3 days before most of the insiders could offload to the retail bag holders. That AI company had the benefit of being attached to the largest technical moat.
The existing AI companies can't even prevent their moat from being distilled by the Chinese token reselling industry.