CP/M and other precursor OSes are really only of interest to historians and nostalgic geeks,
You can say that about DOS too.
it was really the PC, running MS-DOS for the most part, when the vast majority of people were introduced to computers for the first time.
Some, but not "the vast majority". Many people were introduced by pre-DOS computers. Geeks were still buying non-DOS, non-Windows home (and work) computers through all the 1980's, for nearly 10 years after PC-DOS came out. At work as techies we had a mainframe terminal, a PDP-11, and a Commodore PET. We regarded the IBM PC and DOS as for admin people and would not have given a thank you for one. At home I had a CP/M machine and other techies owned BBCs and Ataris, not IBM PC clones. It was Windows that introduced "the vast majority" of people to computers, unaware that DOS lay beneath the pre-Win95 versions. Even at work, most people did not get a PC on their desk until the Windows era.
So, it's not all that surprising that DOS is seen - rightly, I think - as the OS most used at the beginning of the personal computer revolution.
No, that's wrong. The personal computer revolution had begun before DOS and in the 1980s was in full swing with or without DOS. There was a wide range of types such as Sinclairs, Commodores, Amigas, Amstrads alongside the IBM/DOS PC in the 1980-95 period. It was standardised on the IBM PC clone only gradually.