Every nutjob in the world with some out-there theory thinks he's Galileo, rejected for daring to think different. Virtually all of them are, in fact, simply insane.
Yet, there have been brilliant rebels who put their own world-changing ideas on the line, only to end up like Doc Brown in his alternate timeline: humiliated, ridiculed, ignored and/or straight driven to insanity.
You probably know Mendel as the guy who pioneered the science of genetics, and for keeping eighth-graders busy while science teachers watch porn at their desks. Anybody with a high school diploma has filled out those dominant/recessive trait Punnett squares ...
Be honest. How many of you had this explained by a PE coach?
... though astute readers are probably wondering why that technique is called a Punnett square if it predicts patterns Mendel discovered.
What you probably didn't know was that before making his revolutionary discovery, Gregor Mendel flunked his ass out of school and resigned himself to a quiet life as the abbot of a monastery. It had an extensive experimental garden and there Mendel patiently spent the next seven years of his life breeding and cross-breeding peas.
He also hosted a ton of cocaine orgies, but who wants to hear about that?
He carefully documented his work and developed what would eventually be known as Mendel's Laws of Inheritance. Then he wrote it up and got it published in an lesser-known journal, the Journal of the Brno Natural History Society in 1866.
His Genius Was Rewarded By ...
A quiet life of complete anonymity. Mendel's work was read by about zero people, even after he took it upon himself to contact the highest minds of his time by personally sending them copies of his theory. It turns out he would have been better off writing it on a paper bag filled with dog shit and leaving the whole flaming mess on porches.
Why did they ignore him? Because the greatest minds of his time couldn't understand him. It wasn't until 16 years after his death that three independent botanists rediscover Mendel's work and started the genetics ball rolling.