Blender already has a solid and enthousiastic user base before the 2.7 UI update.

Blender was also the forerunner in having a kickstarter-like scheme to raise enough money to make it opensource.

There's an interesting interview between Ton Roosendaal and Blender Guru about the history. https://www.youtube.com/watch?v=qJEWOTZnFeg

The Blender guys were also a lot less hostile towards people trying to make improvements to stuff like UX.

One of the things that GIMP also desperately needs is a name change, while Blender is an odd choice it at least doesn't conjur up sexual images.