He seems to have bet his whole life and at the end he seems to have won. I wonder why he doesn't do a crowd funding, I am sure he would raise the money easily and not have producers on his back.
At first this seems like a non-starter because it's a for-profit film so soliciting donations might be a hard sell. If it were advertised as pre-sale where you are basically buying a copy of the film before it's made, it might work. Still, $120M is a lot of pre-sales and you would be on the hook for refunds if the film were never completed.
Actual equity investors in motion pictures entitled to a share of the profits have to be "accredited", at least in the US. You can't solicit investments from the general public. https://en.wikipedia.org/wiki/Accredited_investor. You also wouldn't want a huge number of investors, that's a lot of paperwork.