The Apple Newton was Apple's answer to the popular Palm Pilot PDA.
Newton: 1993
Palm 1000 (precursor to Pilot): 1996
The first PDAs (functionally, if not by name) were from Psion in the 1980s but started with a calculator-like device and progressed to mini-clamshells with pretty decent (considering the size) keyboards. Apple pretty much invented the "Newton" format. I think the original article pretty much summed up what went wrong. At the end of the day, the main use of a Newton was for diaries, notes and phone numbers - and a Psion did that for a fraction of the price, without relying on hardwearing revolution... er... self-righting pregcognition... darn!... handwaving refutation... (I wouldn't underestimate how much damage that Doonsbury cartoon did - it would have hit Apple right in the target demographic).
Also they forget to include the Apple Mac server.
Had a 9 year run, during which the industry changed.
I think the #1 thing that killed it was the widespread uptake and acceptance of Linux as a serious industrial-strength OS and the general move to open IETF ("internet") standards and open-source server software.
Before then, the XServe was a server-grade machine running MacOS X Server which was officially certified Unix (fun fact: MacOS
is Unix, Linux
isn't Unix - its all about certification and trademark licensing by Open Group) for which Apple didn't charge per-user license fees (unlike many commercial Unixes, MS Windows Server, Novell Knitware etc.) so it really did have a potential market.
Also, when it was launched, the PPC G4 still had some claim to being "better than Intel" - the shine on that wore out quickly, and when the XServe switched to Intel it really became just another Xeon server box.
Not hardware but Apple had it's own version of Unix for awhile called A/UX.
Apple
still has its own version of Unix, called MacOS Ventura:
https://www.opengroup.org/openbrand/register/ - it's been that way since the early days of MacOS X.
Installing A/UX on a Mac took almost a full day of feeding floppies to it.
So did installing Xenix on a PC ~1990 or - a few years later - Linux on
anything. Somebody ought to invent a way of storing data on those music CD thingies.
Of course, if you want
software flops, then every other flop should kneel at the foot of the collision between trains loaded with burning dumpsters that was Copeland:
en.wikipedia.org
...which is why Mac's today run son-of-NeXTStep.