he "created and used a proprietary, encrypted email system"
His employees shredded incriminating evidence, destroyed electronic media, and yet, with all these precautions, the IRS still knows what's in the emails, the codenames of the accomplices and probably much, much more.
Next time the FBI wants to crack an iPhone, instead of once again whining publicly for Apple to put in a backdoor, I think it should call the IRS for help.
That said, given that every time the FBI has whined about Apple, in the end it still proclaims that it got results without the backdoor, so maybe they already do.