Bernie is a populist, in a way just like Trump but with vastly different ideas and appeals. Bernie is not “establishment” - he’s not even a Democrat. Bernie appeals to the people who feel they’ve been left out or taken advantage of ‘by the system’ and so they want to tear it down (sort of like drain the swamp).
My opinion is that many people who support him cannot take responsibility for some of their own decisions; they made choices to borrow and spend, to not save. Some of it may just be they have been raised in a spoiled and entitled environment and now facing the reality of the world they don’t like how it works. The institutions, and parents, have not instilled the ideas of a work ethic or financial prudence. In some respects I feel bad for the kids who are shelling out $100,000’s to go to university and they have no idea what the value of that education will give to their lives. They don’t even know what they will be getting when they commit to 4 years of it, and they are not really equipped at age 16 or 17 to make the best decisions about which colleges to attend. They have been suckered. Education is free. Now with 6 figure debts they can’t get a job that pays enough to pay their debts and their rent and utilities. They can’t save enough to buy a house (or, a house in an area they want to live and work). And Obamacare did not drop the cost of health insurance it doubled it, and tripled the deductibles! So those are the people who support Bernie - the guy promising to take all the burdens of their decisions off their shoulders.
The Democrats have almost always, consistently had the wrong policies to fix problems. Reagan said it best, government is not the solution it is [usually] the problem.
The thing Bernie and the other redistributionists don’t understand is that you can only kill the capitalist golden goose once. Then it’s gone.