That’s astoundingly oversimplified, if not flat out false. ALL of the other candidates dropped out, in the space of six days, and ALL of them endorsed Biden. Including Klobo, who polls expected to win in Minnesota. The only one who didn’t drop out was Warren, who (coincidentally, I’m sure) had many voters that picked Sanders as their second choice. The right wing consolidated, almost overnight. That didn’t happen organically. That was the result of a highly coordinated effort.
Sanders ‘base’ was far bigger than any of the other candidates. He won the popular vote in all three first states, which had never been done before. Biden came in fourth in Iowa, got no delegates in New Hampshire and he got crushed in Nevada. In many of the large states Biden had no pre-Super Tuesday operation whatsoever, because he couldn’t raise the funds. His campaign was on life support. If the ENTIRE rest of the field doesn’t surrender and endorse him, how many states does Biden win after South Carolina? Does he win any states, outside of the deep South? Be honest about that guess.
If you’re saying Sanders didn’t grow his base enough to fight leadership of the Democratic Party, then I agree. But he was by far the strongest candidate, and it took the party leadership consolidating around Biden and telling voters who to vote for - even if they preferred Sanders’ policies - in order to beat him.
This is four month-old history. Don’t pretend people don’t know it.