Gallup and Holbrook were part of the original transcontinental Supercharger route (along with Grand Junction, Moab, Blanding, and Farmington). Tesla was still learning about where to install Supercharger Stations and likely had to take what they could get.
Now, I would guess, Supercharger Stations are prized by the host property owners. Back then, who knew what a "Tesla" was?
Back in 2016 I got a chance to speak to the property owner of the tiny four stall Beaver UT Supercharger Station. He was fascinated by the cars that were visiting his location. Since then: massive expansion to deal with crowds of cars. I gather, from the Beaver thread, that the carwash is coming down to make even more space for Superchargers.
A lot depends on an enthusiastic property owner! I consider the hotel changing hands, perhaps because of the pandemic hit to business, a possible good sign for the Gallup site.
I, personally, would greatly prefer expansion in Grants, to a second site in Gallup.