If you assume that Biden had influence on the prosecution, then we should not forget that the original deal posed by the DOJ was for Hunter to plead guilty to two misdemeanor tax charges for which he would have received 2 years probation, and pre-trial diversion on the federal gun charges.
The judge threw this out, but those are pretty generous terms for what penultimately amounted to guilty charges on 6 felonies and 6 misdemeanors (before all charges were pardoned.)