Anyone who can produce oil more cheaply than the price it can be sold for is making money. Most U.S. producers are high-cost producers, the cheap-to-get stuff mostly exhausted. That’s part of why we used to have to import so much oil, before the fracking revolution. At $100/bbl. you could make a lot of money, but at $25/bbl. a lot of the smaller drillers have gone bankrupt.
This all happened because Saudi Arabia, which produces oil for about $1-$2/bbl. decided a while back to either not cut or increase production. While Saudi Arabia still makes money, they don’t make nearly the amount they need to to keep their country afloat and on the present trajectory, will run out of money in 5 years. The rest of OPEC is in similarly bad shape and don’t have the surplus to ease the pain. Saudi Arabia may have done this to force high cost producers out of the market, to fuck Iran, which is finally able to sell oil now that the sanctions have been lifted, or to fuck Russia, or some combination of the three.
Another factor is that the Chinese economy has slowed greatly and subsequently reduced it’s demand for oil.