Ask yourself this question.
Why did so many Jews live in Poland before the war?
Not saying there weren’t some anti-semitic Poles, but there was no “Poland” during the war.
Because Casimir III the Great was a thoroughly decent man who encouraged Jews to settle in his kingdom and he protected them and all his subjects by egalitarian rule of law.
Neither the Catholic Church’s inquisition nor his neighbors would dare to give King Casimir any lip about his protection of the Jews because he built a huge army of chivalrous knights who could clobber any other army and make it look easy.
As a result, Casimir III turned his nation once broken by war into a thriving economic, academic, and military powerhouse.