The Apple-IBM-Motorola alliance was created in 1991 to compete with the Windows/Intel market. Its main successes were the creation of the PowerPC instruction set, derived from IBM's POWER architecture, and Apple's Power Macintosh line of computers.
IBM originated the idea, having seen that Windows on Intel was out-competing OS/2, and wanting to avoid being dependent on Intel. Apple joined it, seeing the chance to grow out of their existing markets, and Motorola presumably saw it as a successor to 68000, having failed comprehensively with the MC88000.
While the 68000 was used in the Macintosh series, Atari STs and Amigas, all of which sold in large numbers, all the operating systems involved were quite different, so there was no unified software base. That meant there wasn't the sustained demand for 68000 that could have paid for chip development on the scale required to keep it competitive with x86. The engineering workstation market had started with the 68000, but had already switched to RISC before AIM was created.