So, Bernie has 35-40% of the delegates, and 60-65% of the delegates are pledged to candidates that will all back each other over Bernie. That sounds like a brokered convention with someone other than Bernie winning, but the real question is just how bad Biden "fizzles," and when. If he comes out of super Tuesday leading the rest of the 'not Bernie or Warren' group, which seems like about an even money bet, then even if he does this fizzling shortly after he still hits the convention with a substantial number of delegates. In greater likelihood though, if he does come out of super Tuesday leading that pack everyone but Bloomberg* and Bern/ren will drop out and Biden won't actually "fizzle" at all.
What the progressive wing voters just refuse to notice is that Bernie plus Warren runs consistently at around 40%, and 40% does not win under pretty much any circumstance. There's no way that an opposing block that is half again as large splits up in any way that allows him to win, because the convention doesn't go to a plurality, it goes to the larger coalition...eventually.
*If Bloomberg doesn't come out of super Tuesday ahead of Biden I don't know that he stays in either. Donor money could dry up on him very abruptly in that situation and he might not be willing to pour a lot into what at that point would look like it could wind up as a vanity campaign.