Xenix is not so much forgotten as it simply not spoken of because of it being tainted by association with SCO.
Yeah. Management dropped the ball big-time in 1994. SCO could have been Red Hat really easily if they'd had even a tiny amount of vision. Instead they missed the bus, went into terminal decline, and ended up split between Borland (the good bits) and the ambulance chasers from Utah (the bad bits, who everybody remembers).
Caldera started as a legit Linux distro circa 1994-5, but burned through their funds too quickly. As a pivot they bought out Digital Research including their anti-trust lawsuit against Microsoft (for blocking Win95 from running atop DR-DOS). They won big, and the rest is history -- they used a chunk of the funds to buy what they thought was SCO's IP rights, then sued IBM (because that never ends badly, right?).
The next year or the year after IBM announced their big Linux pivot where they went all-in on Linux on everything as a big strategy.
Caldera made all of its money by going into shops with SCO-based point-of-sales or industrial control or what-have-you, and cutting the integrators/resellers out of the loop.
Putting those two businesses under one roof was doomed to failure.