That explains the question:
Was it a real trade? Where the trades real? Answer: no
What was it then?
Answer: A software exploit. This could have happened on many different levels. It could've been a SQL Database attack, it could've been an exploit in the website code itself, etc....
What information is this based on? The current "official" story is that read-only database access was obtained through a side channel.
No further information is needed to explain the observed sales. That is simply the effect of filling every single open buy order.