Pro tip: Whales don't join clubs. It's minnows who school. 
in the altcoin section there are plenty of whales club, there were screen of them talking about the next pump(not know, but in the era where altcoin were profitable, doge era basically...), there must be some club for bitcoin too, i'm sure about it
Yeah, you need a lot of people to create a successful pump - the more the merrier. And if you intend to pump some altcoin, it makes sense to attract as many people as possible in order to make the pump even bigger. You also want to keep those clubs "open", i.e. attract more people to attend the pump. And in the end it becomes one big ponzi scheme, effectively where the people who bought first and sold at the top get most and the others less and less (according to the time they bough/sold, respectively).