I am not sure if i get you right, what do you mean by the email address expired?
Are you trying to say the hacker got hold of your old email address you used to register the account?
Satoshi's email was compromised in the same way
There are some services where your email or account may get expired and someone else can register the same email again. If you are someone famous and your email address is known by others, they won't give you an hour if it's get expired. But I don't know what has happened with this guy. Probably same case.
This just goes to show you that regardless of whether you are the founder or just a regular user, hackers are always looking for any vulnerability they can find and take advantage of it.