If the business model requires hundreds of billions to get the required quality (R&D but also infrastructure to collect data and train, either purchased or rented to 3rd party) while "only" dozens of billions can be earned back (as costs still exist to earn, it's not free once models are trained), then maybe there NEVER was nor till be a good time for an IPO in a rational market.
Unfortunately the market is often not rational in this way.
Hype within retail market means there are suckers willing to buy. Institutional market knows there are suckers when the hype is high. Both would drive the price up, and retail investors the ones left when it falls.