We'll see. What I have found out doing my forecasts is one gets a good idea how independents will vote by seeing how they rate the candidates favorable/unfavorable, in particularly, their very favorable and very unfavorable. History has shown one usually doesn't vote for someone they dislike, whether that is because of ideology, personality, charisma etc. all go into one bucket in determining the favorable/unfavorable rating of a candidate.
Right now, it is all name recognition on the Democratic side. Wait until December or January time frame, then take a new gander at how independents view the candidates and then compare that view to Trump's very favorable/unfavorable.
Yeah, Hillary had the charisma of a wet mop, she came across as aloof and elitist among all her baggage. Then she was lazy and didn't inspire as the turnout percentage of Democrats vs. Republicans was much lower. Charisma does play a large part in our elections, our beauty contests. Obama had it, Romney and McCain didn't, Obama won. G.W. Bush didn't have that much charisma, but he came across a homey vs the two statues, Gore and Kerry. Bill Clinton had charisma all over the place, G.H.W. Bush and Dole didn't, again charisma won. Two who didn't have any charisma at all, 1988, G.H.W. and Dukakis, Bush won. Reagan had charisma, tons of it, won easily over Carter and Mondale. Carter like G.W. didn't have that much charisma, but was down homey vs. Ford who had none and so on.
I think you do have a point where independents tend to gravitate to the candidate who has the most charisma. Or in Trump's case, stands out.
I do believe Sanders would have beaten Trump, my main reason is that he wouldn't have been so lazy in ceding the campaign trail to Trump. From 1 Sep 2016 through 8 Nov 2016, Trump made 116 campaign visits/stops/appearances/rallies to Hillary's 71. In the three deciding states, Wisconsin, it was Trump 5 visits/stops to Hillary's none, zero. Michigan, Trump 6, Hillary 1, Pennsylvania was closer, 8 for Trump, 5 for Hillary. Even in electoral vote rich Florida, Hillary ceded it to Trump 13-8.