> What do you make from someone like Kary Mullis?

By academic credentials, Mullis was a 3rd rate scientist. Then he had that one brilliant invention. Then he went back to being almost a crackpot.

For comparison, the inventor of the fundamentals of the now famous mRNA vaccine technology, Katalin Karikó, was 2nd rate scientist by academic credentials. Could not get tenured permanent position, but was able to stay employed in the normal workforce at a university.

Of course, by scientific importance they are both first rate scientists, because of their important inventions.