I thought this is obvious by now? It's just a show, no one is actually investing such money - this is to spice up the casino and run a news cycle for Trump.
I mean, just check the numbers they are throwing around, there's no such money and Elon Musk even called it out previously in the context of his spat with OpenAI(how much was that $500B on the stargate project?).
Everything is like that, EU is supposed to invest $600B in US but EU's yearly budget is $200B. Qatar is investing $1.2T but their GDP is $200B. Japan to invest in us $550B but they too don't have such money laying around. Saudi's to invest $600B, that's half of their GDP.
This is just part of the show and people figured that Trump likes multiples of $600B, just I wish it wasn't so damaging.