Pandemic is triggering what may be the deepest economic crisis of our lifetimes.
As its most essential level, capitalism, as Marx pointed out, is based on a circuit. Capitalists use their capital to assemble raw materials, machinery and labour-power in workplaces, and through exploiting labour-power, generate goods and services.
They sell these goods and services to other capitalists or to workers, hopefully for a profit, expanding their capital. Then they buy more raw materials and machinery, and hire more labour-power, to begin the process anew.
If at any point, and for whatever reason, this circuit breaks down, a crisis will erupt.