Thinking about the issue i would suggest a few hypothesis.

(1) It is way easier to get an education in a specific field than ever before. (2) It is harder to find new genius level insights. (3) Good stuff eventually gets heard

It seems like a safe bet that anyone outside of a field claiming new insights into the field is probably a crank. Anyone who is not will be aware of the index (http://math.ucr.edu/home/baez/crackpot.html), and be capable of avoiding it.

If someone were to find out something new and amazing, while also being ignored by the mainstream scientists he could go about getting the credentials eventually, or trying to build something useful with the ideas he has.