After Karger et al pentested it...
...it also got a security upgrade. Its security profile was stronger than most other OS's. Although mostly a flop, its combo of features and security did cause some organizations to buy it. The last one shut down in year 2000. It was just too expensive ($7+ mil?) to justify in a market that, at the time, mostly cared about performance per dollar with security and maintenance activities a non-concern. On other hand, Burroughs B5000 and System/38 (later AS/400) were reliability/maintainability-focused products from that era that did manage to survive to present day.