Ostensibly, some topics are off the table because it would upset vulnerable people and we cannot have that. The real reason is that authoritarianism is on the rise on both the left and the right, and shutting down humor is one method to assert control.
Disclaimer: It could legitimately be argued that these folks were canceled for lack of funny, or for anti-Semitism, and not their Nazi jokes, per se. But canceled for Nazi jokes:
