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.
Be careful in following those telegram pnd groups because I tried following one before, and never caught the train. Only the owners of that group can have real benefit of those signals. It is always better to do your own trading tactics and not follow any of those signals or self-proclaimed trading experts. Usually, the owners will tell the info of the coin a lil bit late, when they already had accumulated their coins, so yeah, when people start buying at a higher price, they have the chance to sell theirs.
True! FOMO is more about the decision that are affected by your emotions such as greedy! Those trading signal groups know that, they create the fear of missing out that makes you feel like if you don't catch the train, you gonna loose your chance to earn profit! FOMO is extremely dangerous in trading, therefore, be wise and calm!