I lost TWO accounts to this.
Most recent one again in 2016/17 as I managed, some how, to recover it in 2016 after 4 years blocked, then it gets "to many login attempts" and my existing password no longer works *AGAIN*.
So that's presumably twice that one account got a password leaked out (and the first time I did manage to do an emergency recovery and/or they never changed my pass, just got the account blocked from multiple hacking attempts, and eventually the block expired?).
No, I don't expect it was leaked from a third party website, as I use different passes on each account, and both got locked out. :(