he's only saying that because he happens to live in a super liberal small rural state.
know what happens in most ither states where you don't have name recognition or a party infrastructure behind you and you run for office? unless you have some sort of money reserve you can tap into and dollar bills come gushing out like an oil geyser, it's damn near impossible to not just win but get ballot access TO win. and if you do get ballot access, all you will do is steal votes from the registered democratic candidate (or the democratic candidate steals votes from you) and the republican wins.
a brilliant strategy from a man who twice ran for president as a democrat but refused to change his party affiliation. he didn't even take his own damn advice, and look at what that got us. just the fact that he didn't do this his own damn self should show how stupid an idea it actually is.
and by the way, sure he and aoc are drawing huge crowds. crowds are nothing. how many of those people vote? how many of those people get 2 more people to vote? just showing up to a rally means absolutely fuckall if you don't actually go vote and vote for viable candidates. because if your message resonates with the people enough you don't have to run unaffiliated with a major party because you would have the votes to run and win as a democratic candidate in the first place. because to be very honest, the thing that bernie is suggesting not only sounds like an exercise in liberal grifting, it also sounds like an excellent way to divide a voting bloc that when split has absolutely no chance of beating a republican ever but would absolutely lead to entrenched infighting among a group that should be united in beating republican christian nationalist fascism.