The rules were unfinished. He had tried to do earlier wide scale debt relief that was struck down by the courts. This was another attempt at it and trying to write around their BS rulings. Republicans were already threatening that second version

He’s been focusing on more narrow areas to provide relief because those have been harder to sue about

Biden is still pursuing other avenues for debt relief before his term is up. On Friday, his administration announced an additional $4.28 billion in debt relief for 54,900 borrowers in Public Service Loan Forgiveness — a result of ongoing improvements to the program. Despite not being able to pass broad relief, Biden, over the course of his term, has provided relief to nearly 5 million borrowers through changes to various programs.