Re: How did the auditors miss all that?
HPE shot themselves in the foot for that by putting a time limit on the auditors - they had to complete within a certain time. As I said at the time, I can appreciate the effort to stop them playing the usual game of running up the bill, but in this case that pretty much a got out of jail card for the auditors.
The auditors can simply claim they were not given enough time to go into depth now, even though this alleged level of fraud ought to have been jumping off the page if they'd bother to examine them properly.