It didn't exactly kill it. Wolfenstein being feasible on the PC and not the Amiga, was just a symptom of stagnation. The Amiga (as a promising commercial venture!) had doom (pun intended) written all over it even before Wolfenstein. Commodore ignored the Amiga for years and years.
Edit: I just recalled something - the Amiga recquired either a TV or increasingly rare monitors with PAL/NTSC frequencies. You couldn't just walk in to a computer shop and buy an Amiga and a VGA compatible monitor. It was a flickery and low-resolution monitor or a TV. Not exactly endearing to professionals. I mean, I loved the Amiga maybe too much, it was always the underdog, but it was increasingly also the losing underdog.
A1200 and A4000 could be hooked into a VGA monitor for the flickerless experience. The caveat was that the flicker-free display modes were added on top of old ones, which meant that, while you could run Workbench and most applications on the VGA monitor, all games ran in the obsolete PAL modes your VGA display couldn’t handle. This created a market for niche dual-mode displays, which solved the problem, but were a bit pricey.
I posit though, that by the time Amiga 1200 was out, Amiga as a commercial venture was already dead in the water. The 1200 was a last ditch effort. Still loved it, of course.
I remember that there was some sort of shareware with a 40 day trial that my brother ran, but it stayed at 40 days. They had removed the clock as a cost saving measure on the A1200.
Edit: I just recalled something - the Amiga recquired either a TV or increasingly rare monitors with PAL/NTSC frequencies. You couldn't just walk in to a computer shop and buy an Amiga and a VGA compatible monitor. It was a flickery and low-resolution monitor or a TV. Not exactly endearing to professionals. I mean, I loved the Amiga maybe too much, it was always the underdog, but it was increasingly also the losing underdog.