Biden didn't do it because in the United States of America as it was once known, the government did not release criminal investigation materials except by indicting and trying targets of the investigation. Full stop. That's why the judges aren't going to release any grand jury materials. This is the way we've always done it.
For better or worse, Joseph Robinette Biden followed the rules and norms of the United States of America. Releasing criminal investigation materials outside the context of a criminal trial was a non-starter for Biden and 44 of his predecessors.
Dotard Jackleg Trump has no respect for the United States of America, its institutions, rules, and norms. He was always going to do this to curry favor with the QAnon MAGAts, that is, for political advantage, for himself, as usual. Until he figured out the shit was going to splash on him at least as much as anyone else.