What I mean is that I bought a VPN and I received a free email, then at a later time the promotion expired and the VPN eventually stopped providing me that email, I stopped having access to it and the data in it was most likely erased
So why didn't you change the email address after the VPN promotion expired and they stopped providing you the email? I know that you didn't anticipate something like this happening, but it's a normal security concern to have everything up-to-date in your account. You don't need to have access to the previous email to change it to a new one, all you need is your password.
then at a some point the hacker created that same email and use it to reset the password by email.
How did the hacker know the email attached to your account? Again, another simple mistake: you must always have the "Hide email address from public?" option checked in "Account Related Settings" so that no one can see the email address attached to your account when they check your public profile.
I also wonder how a person can create the same email address provided to someone by a specific service, in your case, the VPN service. If they were to buy the same promotion, they would probably not be allowed to have the same email address as yours.