People dig an efficient car with panache
It's no fluke that over 400,000 people put deposits down on a Tesla Model 3 despite there being nothing truly revolutionary about its engineering. Rather, they've bought into the idea of an efficient car that doesn't break every mirror it passes.
The Isetta differentiates itself from most other cars saddled with the "economy" tag because it doesn't suffer from an economy of personality. I mean, look at it! It could have been forgiven -- and forgotten -- were it just a flavorless thing from the moment you opened the door. But instead, that door is on the front of the car, opening a gateway to a world where fiscal and ecological responsibility doesn't have to be ugly or boring.
BMW makes MINI, so it gets quirky. Rival Mercedes-Benz's corporate sibling, Smart, has been making life-sized Micro Machines for years. The Isetta makes sense here.