And at AWS scale you can always have a human team present to provide a human back up the cost of having 2 or 3 people on an overnight shift is trivial compared to the down time costs.
I wonder why they couldn't do that at OVH. The data centres are always manned and they had 8 minutes on batteries. Why didn't they detect after 20 seconds that generators don't start despite power failure and triggered a manual failover? Sounds like something the staff should be able to do?
