Future prospects for those kids aren't great and there are right-wing grifters targeting the disenfranchised youth. Fascism is a tempting ideology for those who are scared about the future and feel they deserve better opportunities in life. Also being an edgy teen is a right of passage. I've also seen that many many gen z kids care about Palestine, and Kamala told them to fuck off so they did. The ones that see a genocide and don't care tend to lean right.

If the democrats could show a plan to fight climate change, reduce wealth inequality, and stop arming genocide, youth support would slam left like a screen door in the wind. With a broad brush, the older members of the caucus don't see that or don't care.