Perhaps stolen accounts? I doubt every user is practising good security hygiene with a unique password per each account. Password leaks from other sites might well allow a motivated individual to hijack some here.
I could speculate that someone in the past had the business mindset to create thousands of accounts over multiple sites and offers the ability to loan them out for a period of time.
I could speculate that someone in the past had the business mindset to create thousands of accounts over multiple sites and offers the ability to loan them out for a period of time.