I wondered the same. As far as I can tell, in my case, hackers (presumably pro-China activists) simply made multiple failed attempts to log in to my account. They probably had no chance of getting access, but they knew that it would cause the account to be flagged. They probably did not know 1) that reddit did not have my email address, and 2) that reddit required that for a password reset, and 3) that I was not willing to provide it - so effectively they locked me out of my account.