Policies objectively didn't matter. I can't find the link now but when they made people pick the policies they agreed with without knowing whose it was, the Dem policies won like 90%.
If the DNC are not a psyop, then i am convinced they are opportunists. They don't have faith progressives will vote so they will keep chasing the centralists that vote.
If those 15 mil voted third party i bet the DNC would go after them.