ToffeeApple, as a teacher, I'm sure you won't mind if I correct your post a bit!
The IBM PC was first sold in 1981, ran PC-DOS, not Windows. PC-DOS was a custom version of MS-DOS, which was a customized version of 86-DOS, which was developed by Seattle Computing. When IBM visited MicroSoft Bill Gates wanted to sell his MS-Basic interpreter, but IBM was more interested in the OS that they were running. After IBM left, Gates bought the OS from Seattle Computing for $50K, rebranded it and sold it to IBM. IBM actually wanted CP/M from Digital Research, but Gary Kildall's wife was a lawyer for the company and held the IBM reps up while she negotiated the non-disclosure agreement IBM wanted them to sign. They never got to agreement so IBM gave up and left to go back to Seattle. The rest is history!
Basically, MicroSoft reacted to the Lisa, which was the first PC to come with a fully graphical interface. Lisa didn't succeed for many reasons, but it put in place the idea of a GUI as the default that Apple put on the Macintosh in 1984 and has stuck with ever since. Windows 1.0 came out in 1985 as a GUI interface, not an operating system. It ran on MS-DOS. Windows 2.0 came out December 1987, and included Excel and Word for Windows, a port of Word that was first built for Apple and the Macintosh that came out in 1984.
You are correct that the PC took off because of the reputation of IBM. I was in a data center when all this took place and the shift from mainframe to personal computing was done with breath-taking speed. The biggest loss in moving to the PC was the integrity and accuracy of the data. When the data was in the MF, we knew we could trust it to be as accurate and consistent as we could make it. When it was kept in the PC we couldn't guarantee that any report based on it was accurate or consistent. But because of the freedom that the PC gave to the user, it was impossible to put that genie back in the bottle. I spent lots of time in front of my bosses answering the question, "How come the report from the data center says X when Bill and his PC say Y?" In those days CFOs and CEOs didn't understand the difference between the rigorous data integrity actions we took in the center and the way the "Bills" of the world mixed data with no attention to integrity and consistency. To them, a computer report was a computer report.
And you are right, in the beginning the choice of Windows/IBM and Apple was religious in nature. But Apple attracted the creative artists with significantly better graphic capabilities and software, while IBM and the clones focused on business applications like word processors, spreadsheets and presentation software, so the "religious" nature was not so prevalent in business uses because the decision was more rational. In the personal user, however, the choice was more emotionally based. Apple always cost more, and as the clone wars heated up, the PC cost dropped dramatically, allowing the PC to become ubiquitous.
So, there you go, a few tweaks to your post!