the biggest problem is maybe the one who hit that 5.8mil bets don't know about that
All active users are aware of this promo, since it's announced on the notification bar on the game pages. Also, BetIDs are public, so everyone can see if the required bet was hit. I'm guessing you've never visited the website.
and there will be no winner if he doesn't posted on chat after he hit that
There's always a winner; if player doesn't fulfill requirements or for whatever reason isn't able to report in chat, player with next eligible bet gets the chance to claim the reward.
Frankly, everything that panjul07 explained on his "shitpost" is true.