I struggle to think of the head of every political regime in the last century who based his government on stealing money from the rich and giving it to the poor, who didn't end up with a palace. Well, apart from the ones that got killed in military coups and such.

And I doubt the idea that they were all liars that never believed in what they preached would withstand scrutiny.

Suppose, your ethics are unworkable or irrational and you are unwilling to question them. If you think about it, by necessity, you must become more amoral as time goes by. At the very least the luxury of a palace probably helps silence one's moral instincts.

Also, in the original stories, Robin actually was more like rob from the Church and give to the gentry. He was very friendly with the "right sort" of noblemen, he just really didn't like rich priests from the church. So we (in our modern age) have kind of perverted the idea of Robin Hood to fit our times but he never really was some kind of hero for the poor.

See here: https://en.wikipedia.org/wiki/A_Gest_of_Robyn_Hode#Summary