The Biden campaign is like many failed campaigns we've seen before. They're throwing darts against the wall. No focus. No real sense of why it's running its guy for office.
I think Sanders would be a historically terrible president. That said, the campaign knows the issues in its wheelhouse, is focused, and is consistent with what it said in 2016 and pretty much what Sanders has said for forty years. Unsurprisingly, Sanders is doing better than Biden.