What is this "More electable" in Democrats?

The issues that are Trump's presidency is a symptom of much bigger problems we face. Problems that will continue even with a corporate Democrat. Denying this is plain absurd. To make it worse there is this absurd belief that corporate Democrats who call themselves "moderates" are somehow "more electable". This appears to be only propaganda and shown to be plain false by the FACT that the progressive issues being pushed have between a 60-70% approval ratings by the general public and are nothing "radical". The public is for more labor rights, higher wages, higher marginal tax rates, and single payer healthcare. With this fact it is absurd to put forward such an argument. It is absurd and nonsensical to say that Joe Biden is more "electable" than say a Bernie Sanders or Elizabeth Warren. Such a belief seemingly has no basis in actual reality. The people pushing this need to realize that it is not 1989.