Actually, there seems to be no correlation between working hard and becoming the next Airbnb. Working hard is necessary the same way intelligence is necessary: past a certain threshold, other things matter more. And if a metric has no correlation with mega-success, then investing based on that metric is a mistake.
(If working harder was correlated with mega success, then the winners would be easy to pick out: invest in anyone whose team spends all their time on the startup. But many startups do that yet still fail, so it must be true that those extra 20 hours per week shouldn't factor into any any investor's decision making process, counterintuitively.)
Your first and second sentences contradict each other - if hard work is necessary up to a certain threshold, then hard work is correlated with success.
If working harder was correlated with mega success, then the winners would be easy to pick out
The fact that a predictor is correlated with outcomes does not mean it is the sole predictor.
(If working harder was correlated with mega success, then the winners would be easy to pick out: invest in anyone whose team spends all their time on the startup. But many startups do that yet still fail, so it must be true that those extra 20 hours per week shouldn't factor into any any investor's decision making process, counterintuitively.)