Were the (seemingly) Referral Farmers suspended?

[Screenshot][1]

I saw two users coming out of nowhere went at the top of the Referral Rank list for SnackDown 2017 overnight. I thought they were hosting some sort of onsite contests and prompted the participants to register for SnackDown through their referral links.

Now I see both of them kicked off the Rank list. I remember one user’s handle “prof”, so the profile link should be https://codechef.com/users/prof/

What did they actually do, and how did they get so many referral sign ups within such short timespan?
[1]: https://userscloud.com/g6nk54fe2n7y

How can we see referral ranklist?

https://www.codechef.com/referral/snackdown2017

Its for SnackDown

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