it is called FUD and the purpose of it is to try and bring the price down and the reason for it is because they want to buy bitcoin.

the thing is many people know the fact that bitcoin market is still small and can be influenced a lot by the decisions that people make. and sometimes these decisions are based mostly on drama and what they read online. but generally it is from the news they read like the hack news, or some adoption news (as an opposite way which leads to rise) not some random idiot's comment on a forum.
with that mistake they start spreading bullshit about how price is falling so that they can buy more of it.