When you compare Biden to Trump vs. the effects on the Palestinians, were Trump president again, he would not just help the Israelis exterminate the Palestinians, but encourage them to do so quickly- as he’s already told Bibi to “finish it”. So your dichotomy is more than a bit disingenuous .
This is why young people need to vote in every election especially the local ones, even the ones that seem insignificant like a school board election. The only way for a Bernie to win a primary is if such a candidate is not an outlier. The entire party needs to move to the left and that starts from the ground up. Since people need to get exposed to more left wing politicians so left wing ideology becomes more normalized and at the moment it’s not.
When young people vote you get people like AOC and Omar into office. The only way to get a Bernie elected is if there are more AOCs and Omars filling seats in local, state and the federal government. From the school board all the way up to the Senate.