Assuming we are talking about generating electricity at scale, you can probably count the number of private entities with enough cash to finance a project like

Assuming we are talking about generating electricity at scale, you can probably count the number of private entities with enough cash to finance a project like ITER on one hand, and it would be a massive loss to them if it failed. And even if private-ITER worked, you still only have a prototype, not an actual product you can sell. This is not something any VC-investor I know of would risk or can afford.