What if you believe or know that the environmental regulatory environment for fossil fuel extraction is bound to change, or has to change? Say, due to climate change?
Wouldn't you want to at least temporarily stop your competitors from profiting from the last couple decades of massive unregulated oil sales, and at the same time try to dump as much of your product as you could?
I'm not sure Saudi Arabia is willing to sit on theses low prices for decades.
Reg pressure on oil could hurt them too...
Generally speaking the oil available now will be in the future if prices rise again. The technology to access oil has made it easier to get to, not harder.