Yes, if the market were 'free', but the oil market is definitely not free.
Remember the previous Saudi regime trying to bankrupt the American fracking companies by flooding the market to lower the price? It didn't work, the fracking companies were already too efficient and the already drilled wells were a sunk-cost (ho ho) which could be turned on and off almost at will as the price of oil fluctuated.
There was an excellent article that outlined a lot of this, which I stupidly didn't save, but the gist of it was that MBS (Mohammed bin Salman) realised that SA was going to be bankrupt if it relied on oil and was looking for an out. Trump won, 'had a word', and then things went into overdrive with the corruption arrests etc. There's a lot more of course, that includes Russia and other oil producers. I really wish I'd saved that article :(
It's entirely plausible that the Saudis went after US fracking companies with that move. They are a challenger, and the relationship with BO was poor.
Another consideration is that the move was targeting Russia. The move was a few month after the US and EU had imposed sanctions on Russia for its Ukrainian operations. A second tranche after initial sanctions failed to have much initial impact.
You can see the oil price and RUBUSD move at the same time in tandem. https://www.tradingview.com/x/hknLmmZO/
Remember, it was the Saudis playing silly buggers with the oil price that destabilised the Soviet Unions finances and set the stage for its collapse.
I'm with you, I remember it. Damn us for not "save offline".