To be fair both of them probably didn't imagine Stripe would be the one today. You can apply the same logic for any successful companies, like the guy who gave up 10% of Apple for some changes.
There is a difference between not imagining it will be valued at 100B and not imagining it will be 1B+ or a 100M exit.
It is quite likely they knew the latter as relatively low risk expected outcome .
Even at 100M exit, which by valley standards (even in 2010s) is not a lot, 1-2% (after further rounds of dilution) would have yielded 1-2M return . A 200x return for very little downside i.e. a gift .
There is a reason why there is FOMO and little due diligence for really hot startups amongst VCs , most times it is about access to the round which is difficult rather than risk of returns, we only read about the spectacular failures like FTX . We don’t hear about the Stripe, AirBnb, or Figma, OpenAI or spaceX funding rounds .
