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Clearly he couldn't. Not only that but the whole Nasdaq and other exchanges (mutual fund) struggled at doing that. Something is wrong.

Well, that's the point -- he couldn't. He was also trading from a personal account it seems. Seems a bit odd they would allow that.

The rules also allowed a single trader to own 25% of the marked[0].

Futures is not quite the same as 'owning' the market/asset...