(Quotes theirs, commentary mine.)
If you're raising a seed round or maybe even a Series A, you can do it on a great story alone. But once you have numbers, good or bad, they will provide evidence that maybe that story isn't as true as you think.
If you have to let someone go, and they didn't see it coming from a mile away, you messed up.
Set clear expectations, inform people when they're not being met, and give them adequate time to fix.
Some investors will be more helpful than others – but when you're picking between top-tier investors, it becomes mostly a signaling thing. To customers, press, candidates, and later stage investors.
Max did more diligence on Gumroad than anyone else. He asked for twenty references. When he did finally say he was in, it was because he didn't believe the product could have been as simple as I said it was.