Because I could play the same copies of the same games on my Tandy 1000, the IBM PCs at school, and my friend’s Packard Bell. Standardized architecture was, and still is, a huge draw.

Open and documented APIs.

How did PCs beat out the Amiga, Mac and ST with nonsense like that?

I think you can ultimately blame Compaq. It was the first “pc clone” that showed the market that a PC not from expensive IBM was viable. After that even if you weren’t buying a Compaq your own generic clone was “good enough”. So You could access hardware and software built for a $4000 8088 IBM PC with your $1200 clone.

Amiga never was commodity hardware. It was always expensive. It didn’t get cheap enough fast enough. Amiga 500 came too late.

Volume

They couldn’t play Doom (until much later). Even to this day, the Amiga ports are lackluster. Hardware wasn’t designed for that kind of game.

Phoenix BIOS/The BIOS Wars

They could play Wolfenstein and Doom…