I think that happens in the telegram pump and dump groups because when the admin says that they will announce one or two coins in the next 2 hours, people on that channel will prepare their money to follow the pump and dump. The next thing that will happen is people will start to buy the coin at any price after they know what the coin that will get a pump. That can lift the price to the higher price for slow or fast, depend on how people react after they read the announce. For people who don't join in that telegram channel, they will see that the price start to increase so fast, and they will think that the coin will have a chance to grow, and they will also buy the coins faster before the party ends. But people who already have the coin will place their coin at a high price to make a big profit.