Admittedly, it had a partly happy ending, or at least a partly bittersweet ending, even though there was the specter of Nazism.
Still, it was aptly labeled Grim Hotel in the Forbidden Broadway parody. When I saw it with Montevecchi, she got some laughs. Later with Cyd Charisse, it was virtually a laughless evening. But it did have two crowd-pleasing dance numbers and some other brief sections that would be considered traditionally entertaining.
But overall . . . grim. And audiences generally liked it.
It helps to have visual appeal and exciting staging.