[the_fox_says]

They didn't just destroy the hard drives, they went the extra mile and grinded away every single chip in the computers. Their reasoning must be that some chips have a little Flash memory for firmware, which might have been used to store a little data; even RAM chips can retain some data after they've been powered off. Of course that's a precaution that doesn't make much sense in the grand scheme of things: storing data in these areas is technically difficult, inconvenient, and low-capacity (for Flash) or unreliable (for RAM). A person smart enough to pull this off would have been much better off keeping a backup off-site.

They ended up destroying every single part of the computer -- perhaps they spared the keyboard or the display, but that's not likely since they could argue that a storage device could be hidden in there.