Well, Leibniz did a different thing, with a similar part.

What does not go against the hypothesis. Both of their works were heavily subsided by less known researchers that came before them. But it's not clear at all if somebody else would do what they did on each of their particular field. (Just like it's not clear the work they built upon was in any way "mediocre".)

It's very hard to judge science. Both in predictive and retrospective form.