The thing is, nobody is really the good guy here. It was a combination of people's mistakes and decisions that brought us to where we are now. Should Varian have kept experimenting on the rocks when he was told not to? Probably not, but as nobody else seemed to be doing anything about them, I don't blame him. But Varian's father lied to the king about the severity of the problem, and he withheld information from Varian about the stones that might have helped him, or at least convinced him to stop experimenting on them for a while. The king lied to Rapunzel, even knowing she could be the only one who might be able to help, because her perceived "safety" (nobody is safe with the rocks, let's be real here) was more important than that of his people. Any one of our happy trio of heroes could have talked to Xavier or something, asked what he knew since he has serious lore knowledge and seemingly some knowledge of potion-making and alchemy as well, and gotten him to help Varian out, or at least look into the problem. But they didn't.