How exactly, was DEVO a punk band early on in their career?

Punk hadn't hit hardcore yet, once it did you had 25 years of the same guys claiming only hardcore is "real" punk.

They were non-mainstream in the 1970s, weird guys playing weird music, and as such got labeled Punk, despite not sounding very much like we figure punk these days.

A lot of "art rock" was labeled that way, not really that much different than the way "alternative" or "indy" went from being a broad catch-all of styles to being a specific set of bands.

I guess the same thing that made Disturbed and SOAD metal,stupid people who throw labels around like water

The emergence of punk and the scene that grew around it created an atmosphere where people felt free to create whatever music they wanted. Devo came from this ethic, but they were never a punk band.

They weren't a punk band. It was early techno pop.