Bernie has always done very poorly with people over 50 and especially with people 65+ and it just so happens those demographics are the ones who watch and read traditional media the most. And who does traditional media smear or discredit or ignore the most, Bernie, and who do they fawn over and prop up the most, Warren and Biden. That has a large effect on those demographics.

https://www.salon.com/2019/08/16/memo-to-mainstream-journalists-can-the-phony-outrage-bernie-is-right-about-bias/