Study math for long enough and you will likely have cursed Pythagoras's name, or said "praise be to Pythagoras" if you're a bit of a fan of triangles.
But while Pythagoras was an important historical figure in the development of mathematics, he did not figure out the equation most associated with him (a2 + b2 = c2). In fact, there is an ancient Babylonian tablet (by the catchy name of IM 67118) which uses the Pythagorean theorem to solve the length of a diagonal inside a rectangle. The tablet, likely used for teaching, dates from 1770 BCE – centuries before Pythagoras was born in around 570 BCE.
Browsing the wikis, I got the impression research is unconclusive. We don't know if he had a role regarding the theorem, and what it was.
The German version also talks about the various roles Pythagoras might have had or not had regarding the theorem, and how research is unconclusive. One such possibility is that this older Clay Tablet applied the theorem without being able to prove it, and Pythagoras or one of his students could have found a proof.
Also:
So there were lots of meaningful steps one could achieve without actually deriving the theorem. Maybe people were happy to just use math because it works, and a thousand years later someone bothered to prove why.