The same was probably true of the person who leaked Trump's tax returns before the election. Of course they were initially treated with caution, but the media worked to confirm their veracity. Here they won't even ask the question.
I don't think the emails contain anything very damaging to Biden, as far as I can tell. I think the cover-up, lack of care about truth, and blind zealotry is way worse than anything in the emails. I do happen to think the emails are > 50% likely real, but the absolute refusal to consider them impartially is the actual problem, not the emails. It just shows neither pro-Trump nor anti-Trump give a single shit about truth. They just care about winning. Ideology trumps epistemology.