What killed off the Amiga, in the end, was the lack of professional office software. For the managment of Commodore to get their work done, they needed to run IBM PC's. As a result, they grew less and less aware of what made the Amiga a powerful and useful tool. As a result, their marketing began faltering, as how do you market something you do not know? Their sales force was then pushed into the same situation, again due to the lack of professional-grade office software.
Do you honestly think that Gould was playing with the Video Toaster? Or Ali playing with DPaint? Hell no, they're writing up memos, looking at spreadsheets, checking up on the corporate database, all on PC's.
So you want someone to blame for the Amiga's fall, blame the coders that failed to realize how critical this segment of the marketplace *IS*. That failed to grasp that without Commodore's management onboard, the product would continue to languish. Failed to realize how the fate of their platform rested on the necessity of a single, solitary, piece of software, a professional office suite.
