Much of what you say is accurate, but the fact is that in the presidential election the Democratic candidate - the second most disliked candidate in history, being surpassed by Trumpolini - still managed to wi the national popular vote by 2.9 million votes. And there is lots of anecdotal information that some of the disgruntled white males who pushed Trumpolini over the top (somewhat redundant, I know)  found Sanders appealing. That suggests to me that if the Dems get back to representing the people instead of Wall St. and the corporations they wold have easily won both the popular and electoral college vote. So, the problem is not that the Democratic party has moved too far left, its that they haven't moved far enough left.

PS: What you refer to as the "bubble" is where most of the people in this country live.