As @philwelch suggests, it wasn't really a foundry problem.

The Tier 1 Unix system companies (many of whom had been Moto 68K customers) already had their own RISC designs and a lot of the second and certainly third tier companies were getting acquired or going out of business. So by the time there was really a solid 88K product--at least for the server market--almost no one was lined up to design systems around the chip.

Data General did for a while. Forget who else did. But it just never got critical mass.

I mean at some point Apple made it work with their in-house ARM-based CPUs - first for phones then for laptops and desktops. But that was many years later and with a truly massive budget commitment to help the foundries and with enough volume that inhouse designs made sense and with control of the software environment on top. Not impossible but not exactly circumstances available to many companies.

Sun and DEC and IBM made CPUs for their own computers too - but not to compete for basic PCs. Motorola made a lot of phones at one point but not to the degree that they could lock in top of the line fabs.

It's not that the 68000 family was necessarily impossible to use in lower priced PCs by the way. Philips built the 68070 for use in CD-I and other consumer machines. And Apple and Amiga made it work for a while with more mainstream parts.

Sun and DEC very much had vision of competing with PC at times and become the new standard. They just couldn't do it.

The 88000 first came out around the same time TSMC was founded, and long before TSMC became the world leader in fabrication.