Oil futures is a thing investors buy where you pay money now to have the right to buy oil at the current price later. If the price goes up, you can actually buy the oil and sell it at market value, making money. If the price drops, you only lose a little bit of money. In future trading, there is a huge advantage for being the first person to buy a future. No one is investing in oil right now becuase the blockade caused by the Iran war. Over the weekend, Trump tweeted that he was in negotiations with Iran to end the war, which would make oil futures profitable again. After his tweet, a ton of future sales happened really quickly. However, there was also a huge blip before his tweet. The only reason you would bother investing in oil futures before his tweet is if you knew he was about to tweet it. This is an illegal form of investing called insider trading, but it is something Trump has been suspected of doing several times since this term.