We know that the account was compromised because they reset passwords on some websites. We also know that they account was never "deactivated". Most likely it's Satoshi's FPGA order. Just because you have lots of bitcoins doesn't mean you would buy 1000 FPGA's. Why would Satoshi want to mine many more Bitcoins when he owns 1,000,000 of them? He was just tinkering as a hobbyist.
There's no reason for him to use that email account for ordering, though. And by doing so giving out his details to a company, when he can so easily just use his normal and unrelated account.
Maybe he didn't want his "normal and unrelated account" to relate to Bitcoin mining in any way?