From what I can see, Charles Hoskinson is an intelligent person. However, when ambition and greed are involved, intelligence is temporarily suspended. Not all gamblers are stupid, for example.
I think Hoskinson was going to pump up the ADA price with the profits he would make from futures trading. Who knows, maybe he has no money left to pump up the price.
This was the tweet that prompted me to post this, but according to another hive user it could be that he wasn't actually margin trading and just referring to value lost due to price fluctuations.