How do you know that they didn't take positions before they broadcast their intentions on the internet? How do you know that there wasn't backroom conversation offline before they posted or about when to sell? Because they said so? Because it's on Reddit? They certainly don't have to pool their money for it to be illegal. The person who proposed it had positions already and is mainly holding. He made an argument, people thought it made sense, and it took off. There is no sell signal - they are not coordinating when to sell.