It's a genuine legal question that's being decided, because the legal foundation of the loan forgiveness is shaky, at best. Biden had openly said as much.

You're correct that it's not the judges' business to forgive loans, and that's not what's happening. They're deciding whether the Executive actually has the legal authority to do it or not. You're only hearing about a bunch of cases in the past few days because SCOTUS releases decisions in batches, with a large wave coming each June.