It's possible that "it took several years and a small team of programmers to re-write the entire game in C++" because ⓐ those programmers were not as good as he was, and/or ⓑ they had to duplicate the behavior of an existing program exactly, rather than enjoying Bob Ross's happy little accidents, as long as the game was fun.

I'm pretty sure most programmers who are comfortable in both C++ and assembly language can add working functionality to a program faster in C++ than in assembly. Of course, certain C++ libraries will eliminate that advantage, but choosing to use those libraries isn't essentially different from many other bad decisions you might make about how to write a large program.