That's one of those time-honored political truisms that turns out to be based on... not much of anything. Trump made massive inroads with younger voters this time around.

It's all about outreach (and, in the US, Christian youth evangelism.) It's the stated goal of the American right(1) to dismantle public education precisely for that purpose.

1: https://civilrights.org/wp-content/uploads/2024/08/Project-2...