Common knowledge: Doom killed the amiga
Why it's wrong: Doom was released in December of 93. Commodore declared bankruptcy in April 94. There's plain not enough time for an entire platform to go from doing well to dying off, based on one game in about 4 months. (Doom was massively important in fuelling the PC as a valid games platform, but that's an entirely different story)
Before Doom Amiga was well known as the no 1 gaming computer over here in Europe.
Then suddenly Doom came out and acted as someone knocking over the first domino brick, when Amiga users realized they could never have such games quite a lot of Amiga users left! I saw it myself back in the day. To be honest with you even I left the Amiga for a 486 to play Doom :-)