You say, "Windows didn't become a popular development platform after Windows had significant market share. Rather the market share came about in large part because Windows was a popular development platform."
Let me remind you that DOS was actually a popular development platform as well -- with its freewheeling cowboy days of coding directly to hardware and the like. At that time (in the early days of the Mac platform) Apple offered a much more structured development environment complete with tools and widgets (what the Mac then called the "toolbox") unheard of on the PC; but developers accustomed to the "anything goes" PC world rebelled against that -- and indeed they rebelled against Windows in the beginning for the same reason.
So well before Windows came on the scene, and even in the few years thereafter, the PC (running DOS) ALREADY had greater market penetration. Thus it was never about such things as superior API's. Besides, the Mac had a de facto API which the DOS programmers found restrictive and confining.
Why then did developers go with the PC? Developers were lured to that platform foremost for two reasons: First, while more mature software engineers were using Cobal on mainframes and BLISS on Vaxes, the PC programmers then were young hackers at heart who didn't really understand software development methodology and who resented the Mac as a "closed" system. Second, they were lured by the bigger market which the PC platform represented -- yes, even then.
Years later, when the Mac opened its architecture to some degree and was first to reach a 32-bit platform, few developers were swayed because the motivations above still prevailed.
I don't suggest that OS X is an ideal development platform -- it has some maturing yet to do in this regard. However, of those developers fluent in both Objective C and C++, most I know prefer the former over the latter. And I know a number of programmers who have had it up to here with the Windows registry and consider any Unix-based OS to be a much more open and pliable development platform than Windows ever could dream of being.
Also, just as we never hear much anymore about Active X or other MS-developed technologies, today Microsoft itself downplays C++ in favor of its own .Net (which is an adulteration of Sun's Java). Speaking of which, the OS X platform has robust support of Java, and I expect Apple soon to move to version 1.4.2 now that Sun has released it a few days ago.
In short, I don't find your reasoning very convincing -- because I think it fails to take into account that the PC was the dominant development platform LONG before Microsoft took the DEC Mica project and christened it "NT" and long before Gates knew what an API was.