Blender has something else. Loads of money compared to Gimp.
Gimp was designed by open source hackers with no input from professional designers, or seemingly even any interest in their input. It never gathered any kind of momentum as a credible Photoshop replacement for professionals.
And that’s why Blender is getting donations: it’s become a serious part of workflows for all kinds of companies who have a 3D content pipeline. Meanwhile Gimp is still the awkward collection of hackers’ image processing pet projects piled into a clunky GUI that does nothing to enable the things that designers actually use Photoshop for.
Blender's dogfooding efforts were a powerful force in both proving that the software was good enough (to make movies) and demonstrating how it could be better (for the animators who made the movies). I'm not aware of any such efforts for GIMP. What I have seen is roadmaps of what improvements they know they need, and timelines of years to improve core infrastructure to the point that their actual goals are within reach. Meanwhile, other software projects (both FLOSS and commercial) race past them and move on to more exotic and exciting features.
That's just not true at all. GIMP's UI has no redeeming workflow. Even if you master it, you must still constantly navigate it's clunky menu of features.
Blender 2.x had an intentional UX flow. When you mastered it - which really wasn't nearly as difficult as whatever work you were doing with it - you could be very productive.
Blender 3.x didn't really change that flow. It only added some optional visual interface for the people who don't already know the keybinds.
To contrast, Blender has neatly organized every feature contextually. There are specific modes for organizing objects, editing meshes, sculpting, UV painting, etc. that each present their own smaller tailored UX. Everything that is an option (something you would edit with a text box) is under the properties window, in a contextually-organized tab. The entire structure of Blender's UI/UX is organized to match the conceptual UX of the tools it provides.
The Blender dogfooding effort is a reflection of the team’s background in actual 3D production and their commitment to a long-term dialogue with this userbase. Gimp never had that.
I loved Softimage's look ! Flat and minimalist zen design way before ! Then I got the credits for that course and moved on to different pastures.
Their support got the ball rolling and then eventually Amazon and a bunch of big studios threw their weight in but I'm not sure how many of them were involved in the redesign.
https://www.blender.org/about/
4 sources of income: one-off donations and recurring donations (from individuals and businesses), subsidies and co-development funds from businesses, and subscriptions to their cloud service.