I think I agree with you, but my reading of Tolstoy was that his position was more absolutist: the Great Man didn't matter at all, and someone else would be in his place if he wasn't there and that person would make the same decisions with the same results. His metaphor was a herd of sheep that wandered randomly this way and that, and that through the lens of history we look at whichever sheep was at the leading edge of the direction the herd was moving at the time as a "great leader," because the rest of the sheep seemed to be following that sheep.
I do agree that we make a "Great Man" to be much more than they are: that the achievements we ascribe to them would be impossible without support, work, and desire by a great number of people for the thing the leader wants to do, and that this leader can't unilaterally substantially change the course of history without immense support.
Where I disagree is the idea that that person is completely inconsequential; that a similar person would rise just the same, given the circumstances of the time, and that the results would be of no difference.
I'm open to the idea that Tolstoy was just taking an absolutist approach as a method of rhetoric and that he didn't actually believe that leaders have no consequence.