(3) The few ones that have a factual basis and do concern mathematics. I will restrict my attention to these cases as they are the only ones that really answer the question. Now, I am afraid that in each of these stories, where a romantic genius makes a discovery that is ignored or rejected by the conservative establishment of mathematics, my heart is with that so-called establishment, whom I can accuse of no wrongdoing, even with the benefit of the hindsight. Indeed, in none of these cases has been the "romantic genius" been persecuted or even bullied (as was for example Giordanno Bruno, or to a lesser extent Gallileo). We, the mathematician community, have no autodafeauto-da-fé (not to speak of bonfire) in our history to apologize for. What happens in all those cases is that there was a genial mathematician whose works suffered offrom serious shortcomings, and it was those shortcomings, and not the ones of the mathematical community, that made the process of assimilation of these works by the community longer thatthan it could have been.
Lévy, are we said, was a great probabilist, but not very rigorous. I agree with this description. Now is its nonhis work not being rigorous a plus, or a minus? To me the answer is obvious, and I hope everyone here agrees with that. At roughly the same time, Kolmogorov was founding rigorously abstract probabilities on Lebesgue's theory, and this gave his theorems a convincing power that Lévy's have not. The mathematical community has done actually a pretty good and relatively quick work in making Lévy's results rigorous and putting them in the mainstream theory.
Cantor is an interesting case. An absolute genius, for sure, with sometimes almost idiotic remarks -- like when he writes to Dedekind that his bijection between the line and plane refutes the basic idea of dimension. Dedekind kindly answers to him that people working in geometry only consider continuous functions. Now it is perfectly normal and healthy that his works in set theory waswere exposed to such an harsh criticism in his time. There were serious foundations problemfoundational problems in what he was doing. From the important point of view of rigor, he was putting mathematics back to the time of the early calculus, forgetting all the progressesprogress in rigor made in the nineteenth century, and indeed, there were as is now well-known some serious paradoxes hidden in his theory. The harsh criticism against Cantor's work (such as Poincaré's) was the anti-thesis in a dialectical process, where the role of the synthesis was played by lovers of the Cantor's paradise, that wouldn'tdidn't want to lose rigor and admit paradoxes, such as. Hilbert, who were was forced by those very criticismcriticisms to developeddevelop a far-reaching program of mathematics in order to active its goalclear the discovered inconsistencies. Now the partial failure of Hilbert's program (Gödel's incompleteness and inconsistency theorems) shows that there really was something rotten in Cantor's paradise, and the indecidability of Cantor's favorite problem (the continuum'scontinuum hypothesis) gives retrospectively gives weight to Poincaré's criticism: arguably, Poincaré never asked a question which was letterlater shown to be undecidable, unlike as with the continuum hypothesis and theor questions of the gender of angels.
Galois? Well, he has the best possible excuses for having written his genial discoveries in such an unreadable way: he wrote them partly in jail, partly the night before his death, and all before he was 22. Now for the very same reasons the mathematical establishment (the "Académie des Sciences", including people with a very different mind, like Fourier) hashave good excuses not to understand what he had done immediately. And again, very soon after his death (about 10 years after), his work was exhumed, intensely admired and integrated in theinto living mathematics (especially by the German school).