The ugly reality is that the factories put their order in for parts over a year, before expected delivery.
Parts were ordered ( April- June) 2020, for a projected delivery some time in the summer of 2021... makes it tough to adjust for wide spreads in demand.
Just in time delivery, has been the American MBA's management way for years. Inventory costs money to sit on, and it's taxed. Hence the shelves are light for inventory.