Why are Dems so powerless?

Because the establishment Dimocraps do not have the courage of their convictions. Or rather their espoused convictions are really lies they feed their voters while they too are just lackeys of corporations and the rich. The real power is with the latter who control both Parties. But Dims still have to pretend to support we the people for votes and that drags them down. 

Ironically, since polls show that we favor progressive policies, if they actually enacted (instead of just talked about) those policies they'd have the real power of the people behind them which defeats the oligarchs every time. But they're still stuck on corporate money thinking that's what helps them when as Bernie has proven our little donations add up to more than Wall Street's. They are beyond help and progressives eventually will be the majority of the Party and only then will they enact the people's agenda. 

Our long-term strategy then is two-fold: Get the Repugnacon fascists out and get the corporate Dimocraps out. We are making progress with each election but we must remain persistent and patient.