Having two sons in college, what I hear is they blame him for the continued ruining of their lives, in summary. They know lockdowns and masks are bullshit, yet they were forced out of class for a year, parties prohibited, countless games and events cancelled/missed, forced to mask, forced to be tested, forced to get the vax...they pay for gas to get to/from school and around school (they can't afford it now), and they all live on budgets if they have any money at all - and Biden's world costs twice as much and rising. He's made them even more broke.
That is just a summary.
College kids have a laundry list of reasons to hate the man.