If I'm Biden, watching the installation of an administration that says it will be revenge driven, everything that happened before is irrelevant.

It's still a choice, and he made a bad one. No doubt Biden was worried about his son going to jail, with good reason - and perhaps he was more worried about it under a Trump DoJ/BoP than a Harris one. But I don't think it's reasonable to believe that Trump would have done anything more to Hunter than has already been done - Trump won, and Biden's done with politics, and Trump doesn't have much of a history of caring about foes he's already completely vanquished. And if you genuinely think that Trump is going to misuse DoJ, it makes this choice even worse - it might spare Hunter the consequences of that misuse, but it makes it harder for anyone to call Trump to account for misusing the DoJ against anyone else. Biden's basically saying that the DoJ responded to political pressure in prosecuting his son - that his DoJ responded to political pressure. Not a great look for people arguing that DoJ is and should be independent. It was just a bad choice, and a selfish one.