Well, it could also be because Biden's discovery (a) was smaller and self-reported, (b) his legal team helped in resolving the situation, AND (c) the documents have been recovered in both cases and the ball is now in competent authority's court.

It's like this - say you and I both run over someone. I hide the evidence and try my best to prevent my guilt from surfacing. You, on the other hand, co-operate with the authorities and accept your blame. Which story is more likely to linger longer in the papers? I'd say mine simply because I'm being obstinate and refusing to do the right thing as expected by the law and by common decency.

I'd say that's why Biden's story died because of this.