To be fair, he pretty much did collapse between November 2019 and late February 2020 when South Carolina and specifically Jim Clyburn revived his campaign.
The frontrunner status was:
Harris ---> Biden ---> O'Rourke? (maybe for 5 minutes) ---> Harris ---> Warren ---> Bernie ---> Buttigieg ---> Bernie .... then Biden won South Carolina and ran away with it on Super Tuesday, securing the nomination.
I think the main reason people thought his collapse was inevitable is because normally candidates who are thought to be *coronated* haven't done well as of late. Hillary Clinton in 2008 and 2016 for example. She lost one of those primaries and struggled badly in the other. Then of course Jeb! in 2016.
Biden was assumed to be the nominee as early as 2017, so I pretty much think that's the reason.
No disrespect, but your post is incredibly false
Biden was the front for the entire primary except for a few moments.
Never was Harris a front runner. After the first primary debate, she surged in a few early states but never replaced Biden as the front runner in national polling
Beto never went higher than third in national polls. He never had a presence in the early state polling either
Buttigieg was always 4th or 5th in national polling. Did he even break 5% nationally? And he polled 0% outside the early states
Warren tied with Biden in September 2019. She may have polled slightly higher for like a week or two nationally
The only time Biden wasn’t in the drivers seat was after the Nevada caucus when Bernie Sanders was the front runner
