Earlier quoted context omitted.
Unix was under assault from various sides. The vendors were fighting amongst themselves for supremacy. Take a look at Larry McVoy's "Free Unix" whitepaper. https://www.landley.net/history/mirror/unix/srcos.html IBM had developed OS/2, but was unable to effectively market it, in large part due to the intransigence of its development partner, Microsoft, who had other designs. Microsoft was of course pushing Windows NT…
> AS/400 was more an industrial and controls system. Really? We used it a lot in payments. But it was paired up with Tandem and/or Unix (AIX, HPUX). There was certainly a lot of thrashing as mini-computer manufacturers were having their "last hurrah". Thanks!
There may well have been others. I'm not claiming any particular expertise, just general knowledge, from the industry. And being old.