It works for both left and right wing populism. Unfortunately, the former tends to (almost always) manifest the latter. Just look at all left-wing populists who (understandably) hate Joe Biden rolling out the red carpet for Donald Trump.
As a left wing populist, I do hate Joe Biden rolling out the red carpet for Donald Trump
Sure, either interpretation works.
Justifiable hatred of the establishment undermines institutions beyond repair, and since left wing politics are grounded in facts, whereas populism is not a fact-based ideology, left wing populism almost always fails, and populism has become practically synonymous with fascism.
Incidentally, this is also why the left-wing has a tendency for infighting. Again, left-wing politics are broadly driven by facts whereas populism is not. The right wing flourishes under these conditions because none of their beliefs are grounded in empirical or normative reality.
