You don't need to be "corporate" to make promises to constituents you have no intention of fulfilling. Can't think of a single pol who hasn't done it. Not excusing it, just pointing out that the purity brigade comprises of nothing but political naifs and those who exploit them.
You wanna avoid being over-promised and lied to the only solution is to check out of life completely because this is hardly the stock in trade for only politicians but you're especially naive if you think the Bernie cult is doing anything else.