COVID did not shut down Apple's revenue generation. Revenue growth was staggering during COVID. Remember everybody buying electronics because of lockdowns? They may have felt less inclined to pay people while they weren't standing around in genius bars, but they didn't need cash reserves to keep them going.
Having an enormous cash pile is what allowed Apple to keep paying its employees when COVID shut everything down.
Every good company has a cash reserve. The one I work for has a policy of maintaining enough cash reserves to operate for 18 months with zero income. It saved our bacon when the virus came around.