Ton
Blender has structures which go beyond pure voluntarism. Inviting participation from a much wider and deeper set of users and businesses than programmers with a some spare time.
I'm watching Blender very closely and copying or mutating where I can. Asking people to directly sponsor my work, a lot. A seeing what can grow.
@doctormo My outsider's summary of that would be: A lot of networked professionals decided they needed better tools, and better control over them.
Also think about the history of that type of tool. Blender's market saw a lot of closed-source tools dominate for a time then fade away; that is fertile soil for having top talent invest their time in a FOSS project.