I think this is one of the single most valuable lessons any startup can learn. Having been a founder of 3 or 4 startups, and learnt from successes and also from failures, I cannot emphasise enough how important product/market fit and timing is.
Incidentally - this comes from a blog post he actually wrote some time ago that's been republished.
"Finally, to quote Tim Shephard: "A great team is a team that will always beat a mediocre team, given the same market and product.""