Second hand (I wasn't there at the time), but Apple had more than anything a management problem. Managers making a land-grab put everything+kitchen sink into Copland. It was an incoherent mess. Then the VM folks would decide to rewrite the VM subsystem and Copeland would go a month without a single usable build.

Steve and the management team he brought in essentially fired all the MBAs and non-engineering managers. Copeland was doomed by bad management.