The anti rich mentality is a result of an unfair system that is designed to steal from the common person. It's intuitive (though incorrect in many cases) for people to blame the obvious beneficiaries of that unfair system. If we had a more just system in which people were fairly compensated for their contributions to society there would be less animosity towards the wealthy. There certainly are people who want to 'steal from any other class', but disregarding valid grievances by generalizing that characteristic onto anyone who expresses disdain for the wealthy is disingenuous, and ignores the fact that the root of the problem IS the wealthy class stealing from the poor class.
Discussion
There was no shortage of these same sort of people even when the US was on a gold standard. This is not some sort of historical anomoly. It's just that we unfortunately had a political system where those sorts of people were able to worm their way into unearned positions of power & authority & that's why we are in the mess we are in. People never really change all that much. There are always going to be people who are focused on status over everything else. A focus on social status devoid from any desire to understand & create will always result in greed & envy & evil actions.