If his legacy is that of popularizing more left wing views in the US, he’s doing everything he can to destroy all of that and self immolate by supporting Israeli genocide.
To be fair, Bernie revealing himself to be cucked to the demonrats after promising so much likely led many people to realize that the system is rigged against the working class and that the only way forward is to tear the whole thing down.
“Must” as in it is the only moral course of action? Sure. “Must” as in there is something materially compelling them to do otherwise? Unfortunately, no.
This is intentional.