Enterprise (and National) have a very different business model to most of the other big rental companies in that they buy their cars, run them for 3 to 4 years before selling them on.
This seemed to work for them until COVID came along and the madness in the second hard car market started. So as a business decision, they ended up selling their cars, due to the vastly inflated prices they were fetching, only to not be able to then replenish them. Cue a complete lack of stock when you wanted to get a car.
It’s taken a very long time for them to regain a decent stock level.