alt Hacker NewsPer above, it seems like Sun had a core architectural, technical, and engineering failure with SPARC failing to keep pace with x86, and a business failure dealing with the fallout:
> x86 boxes were starting to smoke the hell out of UltraSPARC.)
> we spent too much time trying to help save microprocessor management from an unmitigated disaster of their own creation (UltraSPARC-III, cruelly code named "Cheetah"
In contrast, HP mostly (though it eventually split into two companies) managed to survive Itanium and compete with Dell. IBM continued to evolve Power and its other architectures and still sells AIX as well as Linux systems. Cray still exists as part of HPE. Apple migrated from PowerPC to x86 before hitting a home run with their own version of ARM.
In an alternate timeline, I imagine Sun still existing as an independent company and being the leader in RISC-V systems. But I guess Oxide is something of a successor?
Sun being the leader in RISC-V systems
If Sun couldn't design a good SPARC processor then they couldn't design a good RISC-V processor either. x86 was really their only hope but they didn't succeed there either, maybe because of the same old over-engineering.