I agree there's more to politics than money, but, I think it is fair to say that, whatever legitimate reasons many Democratic Party voters may have had for not voting for Sanders, there is a general media and institutional bias against the Progressive political movement Bernie Sanders represents.

And, not surprisingly, the root of much of that bias is money, in the form of industries which stand to lose (healthcare comes to mind) if the U.S. elected a politician with a Progressive agenda.

Uhm, that's very easy to say, but how is that even possible? Even here in Scandinavia, where money interests isn't as blatantly involved in politics as in the US, most of the media are aligned to corporate interests and vast amount of money are spend by corporations to fund and campaign for right-wing business parties and policies.

Why would Biden need money in competition with Sanders when he got the entire establishment on his side?

There can never be perfect separation, all of society is connected to all of its parts in tricky ways, but part of maximizing that separation is to discover and acknowledge where capital has control of democracy and come up with ways to separate. No ideal is achievable, we can only strive to improve.