My understanding of this has always been that she must somehow appeal to men who like their women to seem like men in drag. There must be a lot of these guys around and a lot of them are (or were) German.
Perhaps.
Considering the vast changes in fashion and style, I can still understand why men thought she was a very attractive woman. And even with the accent, her voice isn't that bad in regular dialog. And the acting wasn't bad for that era either. But they should NEVER have EVER let that woman even TRY to sing.