Hitler is also likely to have profited by his insights.

Lenin was like so many other socialists of his day a great admirer of Robespierre and his party and would undoubtedly have tried to find out how Robespierre got into power and why he lost his hold on France the way he did.

Part of Taine's art was to place himself into the place of the different people and parties who took part in the great events.

When pretends to speak for the Jacobins, it so convincingly done, that it is hard to know whether he speaks on 'their' behalf or whether he is, in fact, quoting one of them.
Taine, like the Napoleon he described, believed that in order to understand people you are aided if you try to imagine yourself in their place.

This procedure, as well as his painstaking research, make his descriptions of the violent events of the past ring true.
Taine knew and described the evil inherent in human nature and in the crowd.