The U.S. Mint produced far fewer coins in the spring of 2020 in order to protect their employees from infection by the coronavirus, creating a shortage of new coins coming into circulation.
Secondly, given worries about virus transmission, even businesses that stayed open and their customers began to favor contactless payment systems.
Federal Reserve head Jerome Powell told a House committee hearing that the central bank believes this to a be a temporary issue and is working with banks throughout the country to remedy it. "The flow of coins through the economy has kinda stopped," he said, but will return to more normal levels as more states allow businesses to reopen.