Somehow I feel like GIMP's lack of popularity has more to do with its reputation for having a horrendous and impenetrable interface than its name.

At one point in the recent past there was a fork of GIMP named "Glimpse," yet weren't a sudden influx of users who were waiting for a more polite name.

I would say both.

BUT, lack of users might just be that it's too late, now. People use web-based tools like Figma, I wouldn't think a lot of people are looking for a Photoshop alternative.