IBM and Microsoft feuding has nothing to do with Macintosh computers, an Apple product. And IBM made PCs. Microsoft makes the operating systems for PCs.
The 'war' between Apple and non-Apple computers began in January 1984 with Apple's release of the first Macintosh. The now famous '1984' TV commercial that aired nationally during the Super Bowl in January (it aired in a few small markets on New Year's Eve 1983 so that it could qualify for 1983 awards; they knew they had something big) was a take-off on Orwell's '1984'. A female runner carrying a hammer - she is shown in color - runs through a gray, drab, uninspired setting passing gray, drab, uninspired human forms, and hurls her hammer into a huge screen bearing an image of a 'Big Brother'-like figure, shattering it.
The message was that the Macintosh was going to shake things up, challenging conformity/Big Brother/IBM. And it succeeded.
So I don't know what feud there was between IBM and the company that made the OS that ran on its machines and the IBM clones, unless IBM had its own software it thought was better and fought to keep it. You can research that aspect if you want.