First of all, they specifically said general election. You're making an assumption that they voted Biden in the primary.
Second, a vote for the green party was basically a vote for Trump in the last 2 general elections.
Third, in reference to your comment slightly higher up on the thread, Biden did what he could to cancel 20k in student debt. The reason it hasn't happened is 100% due to republican lawsuits.
But you just go ahead and keep feeling betrayed.