[mathgenius]

Let's not forget Ludwig Boltzmann, who derived the thermodynamic properties of gases assuming the existence of atoms:

' In 1904 at a physics conference in St. Louis most physicists seemed to reject atoms and he was not even invited to the physics section. Rather, he was stuck in a section called "applied mathematics" '

Things did not end well for Boltzmann [1].

And my favourite, John Bell, who was the first to understand the consequences of entanglement, in 1964. These ideas were met with derision by the mainstream for decades (citation needed.)

[1] https://en.wikipedia.org/wiki/Ludwig_Boltzmann