One reason was that they tried to have both a preemptive OS with memory protection and backwards compatibility with existing OS extensions, which frequently patched OS calls left and right, read and wrote memory across process boundaries, etc.
For example, there was no support for screensavers in MacOS classic; screen savers such as After Dark hacked that in by patching various OS calls. There was no support for Adobe type 3 fonts; Adobe Type Manger hacked that in. There was no support for showing a row of extension icons on-screen as they loaded; an informal protocol was created by various extension-writers to support that.
I know there was more to it than that, but it seems to me that a better managed Apple in some alternate history might have just thrown all the extensions "support" out, shipped, and said there would a better documented API for that kind of crap in the future. Probably also not waste time on OpenDoc because there was no shot that was ever going anywhere if you considered it from Microsoft's, QuarkXpress's and Adobe's perspectives.
Which is basically one of the reasons Mac OS X actually ended up shipping. You got a Classic VM in an OS that otherwise didn't care about making breaking changes, but you had a sliding scale from Classic to Carbon to Cocoa to fix your software eventually. Also OpenDoc got thrown out of consideration very early in the house cleaning process at Apple.
I actually maintained a "Crash Log" at the entrance to my cubicle, recording how many times a given application had crashed that day/week/month/year and ultimately extended it to record even the preceding years.
Quark XPress 6 required a colour-coding which reached into the hundreds for a given year (my recovery folder got cleared out once a week and had hundreds of GBs of files in it most Fridays), and Adobe Acrobat wasn't far behind (but no recover folder), while the OS itself was quite reliable --- work done using TeXshop and other Cocoa apps rarely crashed or had problems.
It was a big change from NeXTstep, where I can only recall one software crash, and two hardware faults (SCSI) during college, which was the high-water mark of my GUI experience, w/ a NeXT Cube (w/ Wacom ArtZ and a scanner) and NCR-3125 (running Go Corp.'s PenPoint) and Apple Newton MessagePad all connected together using a serial interface to write papers and take notes and do graphic design work on.
Yes. Focus is about saying “no.” None of the Copland management or marketing people ever said “no”. So instead of just porting the Mac toolbox to C and a microkernel and shipping that as a first step, it had to have a new filesystem API (so abstract that it will support non-hierarchical filesystems!), and a new OO system for handling text strings, and a new UI toolkit, a new help system, oh, and an OpenDoc-based Finder… A lot of potentially good ideas, but you simply cannot do that all at once.
It wasn’t actually a completely lost cause. They could have shipped it in six months if they’d just simplified the damn thing to a native UI toolbox on top of a microkernel, API additions cut to the bone. (One of the problems with that plan, though, is that product marketing wants all the features you can cram in, so you have to be willing to tell them “no” too.)
Anyway, Gil Amelio and Ellen Hancock also didn’t know how to manage software projects, so instead of fixing what they had, they decided to buy outside tech. Which means we got the iPod, the iPhone, etc. But, in context, they were total dumbfucks; they could have gotten there with what they had.
Gil took over as CEO two years after the Copeland project began under Michael Spindler, and turned it around enough to ship Mac OS 8 a few weeks after he was ousted by the board (after Jobs broke a gentleman's agreement he had with Amelio and sold his 1.5M shares, tanking the share price).
Gil Amelio was not a great CEO by any measure, but he deserves credit for helping save Apple. He uttered the first "no". "No", we are not going to ship this Copeland thing, it's hopeless, we either have to buy another OS and build from that, or sell the company because we're out of time.
That is a bold claim. If they do not know … how can they do that. And a technical solution to exist need management know-how, financial viability or at least the market allow you to play out.
That is why even if you were right, within Steve Jobs there would not Apple.
World need to have a mix or proper mix of important things. The reason why communism fall always not because it’s ideal but because it is wrong in human level. You need a mix. A proper mix.
From the wikipedia page it was that they were just adding feature after feature. As an aside it is very interesting that Classic Mac OS was attempted to be replaced by a microkernel twice but was successful because they figured out how to ship NeXT with fresh paint and an slightly improved window manager that really was just NeXT if you compare the two. (A/UX https://en.wikipedia.org/wiki/A/UX, Copland
https://en.wikipedia.org/wiki/Copland_(operating_system)
As I noted in another comment, it was a remarkable accomplishment that Mac OS X was reasonably recognizable to Mac users and ran the same apps (via Classic and Carbon), all while having a completely different core OS under the hood (though as another poster noted they had prior experience building Mac-on-Unix environments.)
Apple has pulled off a number of surprisingly successful "brain transplant" transitions for the Mac platform, including moving from 68K to PowerPC to intel to ARM. In each case, the user experience remained largely the same and old apps continued to run via emulation.
Mike Paquette wrote extensively about the effort involved to replace Display PostScript (which NeXT mostly wrote) with "Display PDF" as Quartz is often referred to as.
This was the second go at it, they already tried once with A/UX, even though it wasn't as well integrated, nonetheless there was this previous experience.
You missed MkLinux, but of the three (Copland, A/UX, and MkLinux), only one of those was ever slated to be the future of the Macintosh. A/UX was very interesting, but it was also encumbered with a fairly expensive UNIX license and was never really a consideration as a replacement for the existing Macintosh System software. Neither was MkLinux.
