Best case scenario is that HP utterly utterly failed in it's due diligence. Autonomy pre-acquisition was well audited (far as I can tell) and was audited again by a third party pre-acquisition, and also as far as I can tell did nothing wrong in UK law.
HP wildly mis-valued Autonomy (you can tell this by looking at their pre-acquisition market cap), misunderstood their product and completely mishandled bringing Autonomy into the fold; mostly by - from what I've seen - bringing Autonomy into the fold. HP made their own conclusions and only have themselves to blame. If anybody should be indicted it should be the acquisition auditors and it's former CEO. Though I don't think the auditors did something wrong either. HP's board was sold a bill of good by their former CEO and they'll do absolutely anything to shift the blame. Real proof for me is a sizeable class of HP shareholders think that it was all HP's fault.
Really makes a change to see the US criminal justice system abusing wire fraud laws though, oh wait no that's what they do every time they can't find guilt but fancy locking somebody up for doing ostensibly nothing wrong.
If he happens to get extradited there's something wrong with the extradition treaties - people can only work to the law as they know it.