"Show our critics a great man, a Luther for example, they begin to what they call “account” for him; not to worship him, but take the dimensions of him,—and bring him out to be a little kind of man! He was the “creature of the Time,” they say; the Time called him forth, the Time did everything, he nothing—but what we the little critic could have done too! This seems to me but melancholy work. The Time call forth? Alas, we have known Times call loudly enough for their great man; but not find him when they called! He was not there; Providence had not sent him; the Time, calling its loudest, had to go down to confusion and wreck because he would not come when called." -- Carlyle, Heroes, 1840
This is probably the best rebuttal to "leaders are creatures of their time."
The Tokugawa Shogunate had begun to come apart at the seams when Tokugawa Yoshimune took his post in 1716. He breathed new life into Japan, and the Shogunate ran another 150 years.
But when the Shogunate starting coming apart at the seams in the 1860's, no such man emerged. There was no Yoshimune in all of the Tokugawa camp in that decade. The Tokugawa Shogunate is no more.