The consequences already exist, but are not enough to prevent the fraud. The linked article speaks of criminal charges. And here is a CEO going to prison for similar charges of fraud over nuclear construction:

https://www.powermag.com/former-scana-ceo-will-land-in-priso...

Nuclear projects tend to attract fraudsters that are not intimidated by the possibility of jail time.

I would claim that the whole construction industry tend to attract fraudsters that are not intimidated by the possibility of jail time. It is, if I remember right, the largest source of human trafficking in the world.

Who has the truth though?

It's not usually difficult to determine whether a nuclear reactor does or does not exist.

Courts.

It's close enough, and is good enough to generally satisfy our institutions and culture. The standard shouldn't be, and isn't, objective perfection.

In the case of the opening story in the link, yes.

Prediction markets

Good answer, but isn't that a practical answer, based on consensus? Ie its what people believe is true, but might not be actually true.

They are useful for things that become less ambiguous in the future.

Lehman Brothers anyone?