It is, but by getting Lynch convicted they get to blame someone else for their failure to perform due diligence, and I suspect their auditors will be happy to lend a hand because they got exposed for not doing their job.
It's not an either/or issue: HP's auditors screwed up massively by not picking up on Lynch's apparent creativity despite that being their actual job, and Lynch was a tad more creative than the laws allow for. Both can exist at the same time in the same universe.
That HP discovered this retrospectively does not undo the fact that they screwed up on the actual evaluation (and on pricing this beast way over market value to start with), but the hope is that by getting Lynch, err, lynched everyone will look that way instead of theirs.
This is corporate America, folks. If something makes a lot of noise, start looking for what they're trying to distract you from. Also applies to most of the Musk noise - you've seen that demonstrated at their earnings call where "we didn't hit our numbers by a rather embarrassingly wide margin" was shoved aside by talking about yet a new pipe dream that will never be delivered, but investors fell for it. Again.