Have you seen him the last few days?
He hasn't soundly defeated anyone. Without the Super Tuesday dropouts orchestrated behind the scenes he'd be struggling. His Cognitive Decline is getting worse and even people who support him are having a difficult time maintaining their Brave Face.
Oh please!...Joe Biden may be far from your ideal candidate - he certainly isn’t mine - but he’s nothing if not fungible and at least open to influence from the progressive wing while still maintaining a broad appeal across and beyond the Democratic base. Bernie Sanders appeals to a vocal but limited number of whose supporters metaphorical idea of barn restoration is to burn it to the ground with the horses inside and start from scratch instead of rebuilding it from the outside in, one post and plank at a time. Such rebuilding from the ground up, throwing away all of the bad seems appealing at first blush, but a glance at the history book shows that it rarely produces the desired result even when it doesn’t result in total collapse.