There is nothing wrong with saying "X is a good stock, buy it". Saying "I don't really know about stock X, but if we work together to drive prices up we can make money when we dump the stock" is all sorts of illegal.
>"we somehow coordinated and we stuck with it"
https://www.reddit.com/r/wallstreetbets/comments/kwkle2/gme_...
Don't get me wrong. I am not saying a case will definitely be made. Maybe it will be judged not worth the effort or politically unpalatable (going after the little guys). Maybe they had much less impact than they\we think and there was actually some other entity behind it.
But if there is a case to be made, those are the key elements:
* They conspired together
* Their aim was to manipulate the market (move the stock price).