What you are not taking into consideration is the difference between an election and a mass movment. For many voting for Hillary it’s just another election vote for someone they don’t really like all that much. They simply want a democratic victory and sure as heck don’t want to see the Donald in the White House.
On the other hand, Bernie’s backer are true believers who see themselves as part of a game changing movement. They have a blind passion for a cause that can’t be reasoned away.
If Trump win his margin of victory will be a combination of Hillary’s negatives and disgruntled Bernie supporters.