The problem is that the agreement does not seem to specify that the electricity has to come from fusion![1] This is actually common in renewable PPAs - if the specific project doesn't come online then the provider has to find an alternative. But those are usually done with established providers which have > 0MW overall capacity. Helion does not. If the PPA is fixed amount vs fixed price, Microsoft might end up on the hook for inflated wholesale prices instead of cheap fusion.
FWIW I agree with the author of that Data Center Dynamics post, it's quite likely that MSFT and Helion are essentially in cahoots by stoking investors with vaporware. But it also seems like Altman might have sold Nadella 50MW of magic beans.
[1] https://www.datacenterdynamics.com/en/opinions/microsoft-and... This is second-hand, the agreement is not public.
Investors gets ruined on PPAs all the time. With renewables, there's usually some sort of wind turbine or solar park attached, so after declaring bankrupcy the new owners can settle out of court and continue production.
Here there's realistically no way to continue electricity production so the assets will likely be chopped up and sold, if possible. Nobody owns anyone anything and Microsoft doesn't have to pay a dime. They won't get their power of course, but there's no downside for them.
These types articles where a PPA contract is confused with an investment is really common, mostly for nuclear and renewables, but that doesn't make them any more true. Microsoft hasn't invested anything, likely because they know this is (pardon the pun) hot air.