I think the only way to understand Trump is to look at the way American society has coarsened over the past few decades. Things that Trump is saying would not be accepted in a candidate - or even in polite society - in the past. A great many people are angry and frustrated, and we see the worse in the American people displayed by Trump supporters. People are no longer embarrassed by their stupidity and bigotry, and they don't try to conceal it. What used to be defined as serious character flaws are now presented as a valid political position. Trump is the leader of the "anti-s": anti-immigrant, anti-science, anti-education, anti-you_name_it.
Sanders is the only candidate in many years to offer a real option to the status quo. The Democratic Party elite do not like this in the same way they did not like Eugene McCarthy or George McGovern, even though a large chunk of Democratic voters are very enthusiastic about Sanders and his positions on public matters.
Hillary will not offend the Party leaders or their rich supporters. She embraces the military-industrial-congressional complex, providing succor to the moneyed class while proffering the typical Democratic crumbs to the rest of us.