Real, intelligent people for customer support (well, the last time I needed any, which was years ago). You are paying for the service and it's not cheap although also not expensive compared to normal things you also need like Internet service (using US prices). GMail is normally "free," you are the product, and customer support and caring about customers is simply not in Google's DNA. Which we can see in too many of their paid services.

The real protection is to get your own domain which Fastmail of course supports, so you can point it at a different email provider if worst comes to worst, like ajross's plausible proposition that:

"[...] I'd put the odds of Fastmail failing entirely as a business rather higher that those of any single user having an unresolvable 2FA glitch with a gmail account. In the world of real data and not anecdata, Big Tech is incredibly reliable."