So, uh, what's the explanation?
The story appears to be apocryphal. I've heard many versions of it associated with various famous scientists. The source quoted is a collection of jokes, with very low veracity. Additionally, there are no independent versions of the story anywhere on Google. By the way, the quoted date of Sommerfeld's death is also incorrect. I wonder if there even were (unpowered) ceiling fans in Munich's trolleys during that time.
Another monthly installment of the rationality quotes thread. The usual rules apply: