Blender has always been ran with a strong priority of being/becoming a software that is used by many professionals world-wide, and Ton Roosendaal has been there

Blender has always been ran with a strong priority of being/becoming a software that is used by many professionals world-wide, and Ton Roosendaal has been there since day 1 to push for this. They have actively sought to find ways to hire many people to work on Blender - from code, documentation, management and outreach/marketing. This is quite unlike most other open source projects in the libre graphics community (like GIMP, Inkscape, etc), which are run by a loosely organized group of people doing this primarily as their hobby or side-project. That some GIMP devs now get a bit of money is actually a quite recent development. So over the lifetime of GIMP and Blender, Blender has had many more manhours (10x?) dedicated to it - and more product/market focus. Though developed very differently, both are quite successful open-source projects, and widely used. Disclaimer: I got some commits in GEGL/GIMP. EDIT: Krita, also mentioned here, is developed more in the style of Blender, with Boudewijn Rempt being the key facilitator.