>Even if you are able to categorically claim PMF, it doesn't guarantee business success. There are a fair number of startups that are able to build out their product, raise investor funding, and gain early traction, only to peter out and never reach growth stages.
To me it seems obvious that these startups achieved PMF only in a small subset of their target market. That is, they misidentified the market in which they had achieved fit and/or did not conduct an adequate segment analysis.
A great many things can still go wrong, even with a great product and PMF. The business economics don't work. The leadership make some catastrophic decisions. A competitor eats your lunch. Etc etc etc.
To me it seems obvious that these startups achieved PMF only in a small subset of their target market. That is, they misidentified the market in which they had achieved fit and/or did not conduct an adequate segment analysis.