"Why did the company not hire more people?" COVID dramatically reduced worker demand for airlines, hotels, restaurants, the like. So those people went to do so

"Why did the company not hire more people?" COVID dramatically reduced worker demand for airlines, hotels, restaurants, the like. So those people went to do something else, something that saw an increase in demand, say delivering packages. Now those workers are needed again, but no longer available. Or only a few. As an example, at Schiphol airport (Amsterdam) they require 500 new/extra security staff. It takes months to find them and just training takes several weeks.