The price of oil never went negative. Investors bought oil contracts at fixed prices, when the cost of oil dropped heavily, those contracts were worth negative $$, so they had to pay people to buy their contracts. Let's say you think the cost of apples will be 15$/bushel in June, so you make a contract to buy them at 12$/bushel in order to make profit by selling the  at 15$/bushel when the time is right. You don't have an apple juice store, you don't have anywhere to put the apples, you just own a contract guaranteeing that 12$/bushel number in June. Your goal is to sell that contract to someone with an apple juice store. Now let's say the cost of apples drops to 7$/bushel in June. What can you do other than sell the contracts at a loss? That's what happened to oil. The price never went negative, people who buy oil contracts on futures had to pay people to take those contracts off their hands.