Why didn't the Jews do more to resist the Holocaust?

The answer to that would be a question; to defend themselves from what? The victims were often not exposed to the face of their persecutor until they were under armed guard and it was too late.

Having said that; there were some conditions under which the Jews were forewarned enough to mount some resistance, like the uprisings. But most of these had to occur once the victims were already incarcerated.