"Increased oil supply -> Lower oil prices -> Everything gets cheaper to make -> Increased economic activity"There would be increased economic activity if businesses don't close left and right because of a combination of decreased demand and supply as both consumers and workers self-isolate and live in quarantine, and the knock-on effects of China's reduced manufacturing capability (soon to be followed by reduced manufacturing capability of much of the rest of the world).
This stock market crash is just the tip of the iceberg.
The tops of political, administrative, business, and military hierarchies tend to be overwhelmingly old, and most susceptible to succumbing to this outbreak. As many of them die, as the bodies they govern are plunged in to chaos and societies around the world go in to crisis mode, the markets will respond even more adversely than they have already, as the markets don't like uncertainty, and there's no end in sight to such uncertainty for the foreseeable future.
There is little economic upside from this pandemic. Few ways of profiting from it except by shorting nearly everything and buying gold. The bond markets and treasuries are also likely to suffer as governments default.