As opposed to 0.999999% of the human population who can't do it even if their life depends on it?
I believe even Wiles in a documentary described his search for the proof of Fermat’s last theorem as groping around in a pitch black room, but once the proof was discovered it was like someone turned the lights on.
Then they can train a network to evaluate intermediate positions (score network) and one to suggest things to try next (policy network).
So they had three days to keep training the model, on synthetic variations of each IMO problem.