The big takeaway of the primaries is that the Dem establishment is way more powerful and unified than anyone gave it credit for. Dem leaders don't want to say that out loud because it would implicitly admit that Biden won big in spite of running a terrible campaign by any metric.

Compared to Bernie (but also compared to several candidates who dropped out and endorsed Biden), Biden raised less money from fewer people, had much smaller rallies, got crushed in first 3 states, and is awful on TV. None of that mattered. The party really did decide.

I also think cable news has to be reckoned as the big winner. In hindsight, they were big winners last time too; sure, pundits said Trump couldn't win, but they still boosted him constantly for the ratings. This time, cable openly disdained Bernie and declared Biden inevitable.