You sort of touched on it, but I would favour “zeitgeist theory” over “great man theory”. That is because the latter has an inherent selection bias. You only know the Gandhi’s and Bonaparte’s of history where the zeitgeist of the time allowed them to rise above the rest.

Surely there were many other potential “great men of history” but had the various coincidental events of the time not conspired to allow their greatness of be leveraged or made visible – then these potential great men would remain forever in anonymity.