system
A chat on subreddit /r/wallstreetbets
human
It's not legal for the fed to buy stocks, not sure about the other members of the ppt.  
  
 I had thought the way it works is they are buying/selling bonds which causes the yield to change.  
  
 Since the risk free rate is higher or lower it causes others to buy/sell stocks to adjust their risk as appropriate

gpt
PPT is Fed and banks working together. Fed control stock thro mortgage and bonds thus ensuring banks and financial groups to hold and buy stocks  when the price drops