Do you know that they spent a lot of money on high level language development so they didn't have to rely on someone writing a complex assembly language for the software for those projects?
You're missing the point.
All I'm saying is that it's possible to handle a large project in assembly language and get it right. Possible, nothing else. In fact, it probably isn't easy. Large projects aren't easy, and assembly language will obviously not make them any easier. Doesn't mean it's impossible. Difficult != impossible.
Furthermore, 68k development is a hobby. As such, choosing assembly language on a 68k system is something you do because you like working in 68k assembly language, not because it's the least difficult or the fastest to develop in.