the fatigue element is one reason why it might be difficult to be a fast bowling captain. however, i am not convinced that that is the main reason why there has been a relative dearth of fast bowling captains relative to captains who are batsmen.
the socioeconomics of cricket (including other demographic factors) need to also be considered. for example, in the not so distant past, the gentlemen generally batted while the miners and the blue collar chappies provided the brawn....obviously, the establishment wasn't going to let that sort end up being captain and represent the empire, now, were they! am being a bit flippant here, but the point stands.
on top of the class aspect, reinforced tropes of the sort that the psychology of the instinctive (brawn over brain) fastbowler was not conducive to the analysis of the ebb and flow of a game were also quite commonplace and served, rather well, to maintain the status quo on who did what, so to speak.
in places like india, spinners generally ruled the roost, and so there were very few fast bowlers from which to even have a captain.
just a few important points that need to considered along with the argument relating to the energy expenditure aspect of fast bowling as being the prime obstacle to the fast bowling and captaining thingy...