As usual when you take a dismissive stance ("this is obviously a waste of money!") you are ignoring lots od details. The use case of a mail carrier is not well suited by a massive eSprinter. They have no need for something so large. They want to be seated at the height where most mailboxes are so they can make many deliveries without getting out of the car.

Whenever you find yourself going "why would they make THAT decision?" assume it is yourself that is ignorant and take it as an opportunity to learn, rather than dismiss the choices of people who specialize in the area you are puzzled by.

I used the eSprinter as one example, not the only option. Maybe something like the Ford eTransit or the Rivian EDV is a better fit for postal deliveries. My point is that other delivery companies and postal services use commercial vehicles, most likely because that's the most cost-effective option.

Considering the NGDV's atrocious efficiency, lack of hybrid option, and high unit costs, it seems far more likely that this is a pork project for a defense contractor than that everyone else is doing it wrong.