A hacker could have also traced the IP address of the specific computer that created the account and tried to hack that computer directly.
Except that hacker wouldn't know the IP address of the computer that created the account, only AnonSteem would know that. And if Anonsteem wanted to compromise the account, they could do so easily: just make a copy of the private key.
That's what I was saying I thought :D
I was giving AnonSteem the benefit of the doubt that they wouldn't preemptively compromise accounts.