Well, except for getting a pre-release version of the crop report…and falsely imprisoning Clearance Beeks. But the crop estimates should have been available to ag commodities analysts weeks before the crop report came out. It’s a bit of dramatic artifice necessary for the story but not remotely plausible. And of course someone would come and bail out the Dukes before they got a margin call (which wouldn‘t have happened at the end of the trading day back in the ‘Eighties because of the time it would take to reconcile trades, and I don’t think would even happen today) just as happened with the Hunt Brothers and their attempt to corner the silver market that the plot of this film was very loosely based upon.
ETA: here is a better explanation than I could do:
Stranger