A few months ago, geteso (previously known as esoTalk) allegedly suffered a breach. While the nature of the breach is not known, what is known is that accounts were compromised (resulting in the website mandating a password change for all user accounts) and email addresses connected to user accounts were flooded with password reset requests from the site. The identity of the perpetrator behind the breach is widely disputed amongst its community.
What likely happened here is that someone spammed the everlasting shit out of this forum's password reset system using email addresses obtained from the geteso breach. This means that anyone who used the same email address to sign up for geteso as they did to sign up to this forum would get absolutely buttfucked by email reset requests. This appears to be what happened in your case.