No people really did not like Bernie that much. He was making a lot of promises that he did not have the political capital or chops to deliver on; and a lot of people saw through it.
Not to mention that his cohort of rabid online supporters were as insufferable as those supporting the orange man; thus giving his campaign a similar kool aid drinking cult vibe.
As far as the talk about other candidates forming a coalition against him … that whole line of argument is pretty laughable. This is politics. Success in politics is achieved by building coalitions among constituencies and their representatives to advance policy.
If Bernie were such an effective politician then why was he unable to get someone else to stay in the primary to split the establishment vote?