I could have just fallen prey to exactly the flaw that you're describing, but if I look at Apple during the Sculley years and immediately prior to Jobs' coup vs afterwards, I think that the company changed direction and the subsequent progress was by no means pre-ordained in 1991-1997.

Likewise, Microsoft during the early Gates' years was not a lock to rise to the level it attained.

Or the Buffett Partnership and eventually Berkshire Hathaway under Buffett.

Maybe these are outliers (and by company size/outcome, they quite obviously are), but that seems to itself be a (perhaps circular) argument that leadership plays a significant role in directing the trajectory of the company.