It seems you are assuming that execution is done mostly by technical co-founders. I would argue that many crucial aspects of what we categorise as "execution" are non-technical business aspects.
In my opinion business factors like hiring and ensuring funding are way more important than having a superior product. Betamax was technically superior compared to VHS, Amiga OS was a better product than DOS, etc. etc.
Other non-technical factors, besides the ones you mentioned, are related to company culture, sales, HR and talent retention. Just a few examples that I can think of right now, there are many more of course.
