I am pretty sceptical too as well mate. A lot of chat will be that Usmanov is funding this so we can't do it in a transparent way. However I'm not entirely sure who owns the Stadium, us, 3rd party or LCC. That is quite important. Within my lifetime LCC have been close to Bankruptcy. If that were to happen (not wholly unrealistic in post brexit Britain) and a liquidator came in we would be in a challenging position if we were paying them back.
Likewise if it's in Unsmanovs company (or Moshiri's name) what happens when, nicely putting it they die. There's no guarantee their heirs will want to give Everton a stadium for nothing.
That would be the key risk in all this for me. We look ok for 40 years. However the question of how we pay off the 300 million capital is important. Coventry did something similar I think, and once they fell out of the league it all went sour quickly.
That being said, it could be that Usmanov/Moshiri have lent us the money, so we own the assets and owe them 300 million quid. While not ideal that would be a very good outcome and I hope it's the one we have. I'd rather be left with the asset in our name and owing money, than having the asset in someone else's name with the promise of being able to buy in 40 years.