He chose not to prosecute Hunter Biden. Not choosing to do this was not something he had discretion over. Barr had a duty to initiate and pursue prosecution in this.
The AG is not a political advisory role. The role is laid out in manuals.
The AG, like all Cabinet Officers has to have jurisdiction over matters they are asked to execute. They have discretion over prioritization. They do not have the right to ignore matters that are squarely in their scope of of duty.
The entire Biden family has all the characteristics of a set of dupes who have been put in place as U.S. intelligence assets.