Wrecking the workstation market was easy, because workstations had small numbers of CPUs, and small pools of RAM. Intel started fucking up that market in the late 1980s.

x86 wasn't competitive on the server side until K8 (AMD) and Nehalem (Intel).

So you have a real long stretch -- 1987-ish to 2008-ish -- where proprietary UNIX on proprietary architectures owns the server side, even though the workstation market is eroding the whole time.