Which global health emergency was the main catalyst for the 2020 stock-market crash?

The COVID-19 pandemic was the main catalyst for the 2020 stock-market crash.

As the virus spread internationally in February and March 2020, governments introduced travel restrictions, business closures, and stay-at-home measures. Investors rapidly repriced expectations for economic activity, corporate earnings, energy demand, and financial stability. Major stock indexes entered a bear market at exceptional speed.

The crash also coincided with a sharp oil-price dispute between Saudi Arabia and Russia, which intensified pressure on energy companies and markets. Central banks and governments responded with interest-rate cuts, asset purchases, emergency lending, and large fiscal programs. The health emergency was the catalyst, while the speed and depth of the market move reflected both the economic shock and the structure of modern financial markets.