This is, of course, making the wild assumption that Strange had actually learned EVERY spell that ever existed. Which he hadn't.
In this scenario, he might (read "WOULD") make it his goal to discover time travel spells that hadn't yet been utilised.
As I've already said, in this scenario, the snap happened, so Strange must have voluntarily handed the Time Stone to Thanos. That's MCU canon. An undeniable fact.
For Strange to have done that, he HAS TO have seen a future in which the heroes win. That's literally the reason he gave it away. Ergo, the future in which he saw the heroes win literally MUST happen.
But, as I've now stated more than once, this is the future in which they do get that inspiration. It might only be 1 in several million again, but it's the 1 in which that happens.