Biden doesn't have an energized base. He doesn't even have a base. What he has is the structures of power instructing the public to vote for him, in order to avoid Bernie.
But do not forget: It took 30 years, three campaigns, and the entire force of the media and American oligarchy to make Joe Biden, rapist and segregationist, win a single primary.
Bernie's support is with those you actually need to win the election - those who do not vote, those who are alienated from the political establishment, and also nearly every demographic under the age of 40.
Biden might be made President, if he remains technically living enough to be awarded it, but it will be an award - even Trump earned his victory more than Biden ever could. It will be a victory of vast uncontrolled forces happening to array against Trump, a victory of black swans. And if Trump manages to get that UBI thing passed somehow you can say goodbye to even that possibility.
The fact that Bernie has done as well as he has with everyone with power to throw around trying to get ride of him demonstrates his viability. Joe Biden had to be literally given Buttigieg, Klobuchar, and Bloomberg's campaigns to get anywhere.
Just remember: Trump is good news for the powers that be. Biden is merely acceptable news. The help that he's been given will evaporate should he survive to become the nominee, and go over to the White House instead.
Have fun winning an election with just boomers. However many are left by November, that is.