Hmm,thats the thing about history, the longer ago it happened, the more reasons & "hindsight" emerges. But like everyone here, I do agree that the Amiga died in its classic form when CBM died.
As to what exactly "killed",it off? There's a number of things which affected it in different ways.
A) CBM mismanagement. Very obvious. Despite CBM's presence & success in the days of the C64, the Amiga never really succeeded in the U.S as a gaming platform, although ironically it did seem to achieve professional recognition which it lacked elsewhere,though as Twistin' would attest,it was never because of good CBM support or management/marketing!
B)Lack of R & D. The original Amiga was & always will be remembered for being a remarkable landmark in powerful home computing,which spoke volumes for how long it lasted & took other platforms to catch up & pass it. But again,because CBM made the disasterous plunge into the IBM PC market just when that market first began to crash in price, the management just sat on their butts & refused to develop the Amiga. Despite the best efforts of their R&D teams they never received the support they deserved from upper management.
Unfortunately,by the time efforts on designs like the ill-fated AAA chipset & even the RISC developments started,there was no money left to see the projects completed.
Although the AGA development was an improvement, it was nowhere near as good as that was promised by the David Haynie led AAA project,(Or so we were always promised in the Computer magazines stories.)
I always regarded it a great shame that one idea I'd read of their future dev. plans were to converge the Amiga/PC & have a true multimedia multi O/S PC. Who knows,if they'd ever done it,we may not be debating here today...
And C) Sega & Nintendo. Once the 16bit consoles flooded the European markets with big marketing,cheap console prices & reduced piracy,it killed off the last Amiga stronghold in Europe where it was at it's best as a gaming machine with some great developers.
Though I do have some sympathy for CBM's agnst over how to "push" the machine. Unfortunately,it was a victim of it's own success. After all,on one hand you had a powerful true multitasking multimedia machine capable which existed before there ever was a "multimedia" machine/market out there, but on the other hand you had a top gaming computer that had jaw dropping titles like Shadow of the Beast,Lemmings, Defender of the Crown,Battle Chess,etc. How do you market a machine that can be a "serious" business machine & yet be a gaming beast too?
The saddest thing to my mind is that the gaming industry has never been the same since the home computer market of your C64's Amiga's ST's etc. died. A lot of home-made development teams emerged with funny, original titles which you never see anymore in this 3D FPS market thats about today. Even sadder is that a lot of those same development teams/publishers died too.