Mmm...yeah so someone who learned German as a second language and knew a lot about the culture and history explained the toothbrush mustache, as worn by Adolf Hitler.

"So it was because German elite airmen needed oxygen at the altitude at which they flew, within the airplane. I suppose because the cabin was not pressurized. They had to be able to get a good tight fit on the masks, so the only facial hair they could have was a toothbrush mustache, because that didn't make the mask leak.

So in solidarity with elite airmen, to show they were just as masculine despite having so little facial hair, Hitler wore that mustache always."