Typically organisations that employ controllers are driven by someone who watches a spreadsheet. Activities such as COVID, 9-11, contract renewals always concentrate the mind on the bottom line. Little relevance is given to the time it takes to train and the actual number of seats available to train in. This latter is normally the major problem.
Years ago we were training controllers in a European country and were told how many we had to provide classroom/simulator training for that year - All for one tower. It turned out that the actual On Job Training capacity was about 10% of the numbers receiving basic training.
Sadly the magic solution is always some years back - bean counting rarely looks further than the CEO's KPI's and bonus needs and normally they have moved on (with bonus) before the crises occurs.