Your ignorance makes me pissed off, and obviously I have no words to describe your ignorance.
Ponzi schemes are illegal when hidden behind investments in order to deceive potential investors. But when it's stated (and visible to all), paying and not using words such as "investment" then it's legit and legal as well.
Do you wanna know how I know it? I'm in close contact with my my lawyer (whom is one of the greatest here in Italy) and penalist who are morally against Ponzi schemes but not for those treated as games, because it is actually considered gambling.

By the way, I don't see any evidence of scam or complain against it even though iz-nop naturally collapsed (according to their rules), so dulcis in fundo it operated legitimately.