the question was asked elsewhere : "How did this narrative gain so much traction? And who gained from it?"
I would guess that since the search for truth is privatized in for profit news outlets that are experiencing failing business models and with 24 hr news cycles that the pressure is on to deliver 24 hr infotainment. you can have your news (or any product) quick, cheep and good, but you can only choose two, as they say. The sensational news header: BREAKING as click bate. the drip drip drip of information surfacing in the ongoing Trump/Kremlin investigations feed a collective connecting of the dots to establish an accurate narrative.
desperation must certainly had set in for team HRC in dealing with the Never Hillary clusterfuck shitstorm of distortion and disinformation coming from right and left as well as the realisation of self inflicted wounds and campaign miscalculations. + aysemetrical wiki leaks, Steele's quasi-substantiated dossier leak, pizzagate, russian $ trail, trumps lies (incl election fraud claims), republican obstructionism, voter supression, Killlary meme, bad health meme, Comey x2, Giuliani/nyc police/nyc fbi...