I recall on a visit to China that a large number of Chinese who ride scooters were using electric scooters. They would lock up the thing at street level and take the battery in for the night to charge. With tens of millions of people in various urban settings where scooters are their affordable means of transportation, this has to have a decent impact. Modern battery tech has probably gone a long way to making this feasible too.
It’s not so much reduced demand. The real answer, though, is that Canada’s tar sands (the oil industry would prefer the less ecologically alarming “oil sands” - they’re tar) and USA fracking have added greatly to the world supply. Thanks to fracking, the USA is apparently once again the world’s largest producer of oil. (But IIRC still a net importer, just not as much).
Why would Saudi Arabia reduce production? It’s a trade-off. The idea is to reduce production and keep the price high; but the non-OPEC sources will likely fill in the void, so even if the Saudis cut production, others will just move in and sell more. The Saudis have an extravagant economy highly dependent on oil revenue, already going into the red. Cutting production makes the problem worse. Their attitude now is why should they take the pain so others don’t suffer? besides, even inside OPEC, typically when the Saudis cut production, everyone else cheats and sells more than their quota.
Since Saudi oil is already developed, pumping it out of the ground is close to pure profit. Other producers need to spend a lot more to steam or frack their oil out, or drill in deep seas, Siberia, and other inaccessible places. Saudi Arabia is hoping by letting the price drop, these producers will close shop or at least stop investing in more production.
The fact that it conveniently punishes Russia, who gets much of its foreign revenue from gas and oil, is a bonus. USA is happy, they want to teach Russia a lesson over the Ukraine. Saudis are happy, they want to teach Russia a lesson over its support for Assad in Syria. Iran is another Saudi antagonist who needs oil revenue more desperately than the Saudis, still more bonus. Low oil prices screw over Venezuela, an antagonist of the USA. More friendly countries - like China, Japan, the EU group, etc. - benefit from low oil prices. Life can’t get any better.