1) the Democrat party hates economic populism. Bernie would have to hijack the party like Trump did. But where Trump has many allies in positions of power, Bernie has none.
2) the populist rhetoric that people like the most is false. Grocery prices aren't high because supermarkets suddenly got greedy. Worker exploitation isn't why billionaires exist.
I also don't think it's good strategy blame a minority group for all the problems in the country. Billionaires are not a protected minority obviously, but when you stoke anger against one group it can easily result in a different group getting unjustly targeted (Mexicans, trans people, etc). We don't need any more of that and politics of hate and resentment isn't the way forward.
Or - if you accept this as the obvious bullshit that it is - then all that money is not a fair compensation for anything, but rather the consequence of being in a position of economic power that makes it possible to extract wealth from the economy in one way or another. How exactly said extraction is done is immaterial - if the wealth is unearned, it means that it was taken from someone else, since someone ultimately did the work necessary to create it.
Advocate for higher taxes if you wish, but acknowledge that economics are not a zero-sum game and propose an alternative to savvy investment, unless you simply want to foment division or to upend modern capitalism entirely.