The weird thing about the PC series in general was how much of a afterthought it seemed to be by IBM. It wasn't world-beating at launch,, and it used a huge amount of off-the-shelf and bargain-basement kit so they could get it out quickly.
It sold like hotcakes almost entirely because it was a trusted brand. The concept of "documented architecture where you can easily expand it" helped, but plenty of other systems had similar offerings (S-100, for example).
So they figured "people will buy whatever we sold"-- so they tried to move down into the "home computer" market with a machine that was more expensive than a real home computer like an Atari 800XL, not perfectly compatible with a real PC, and which hit the market pretty much just as PC clones, offering better specs for the same or less money, were beginning to flood the market.
I wonder what would have happened if they had held off til, say, 1982 or 1983 to release their PC. I suspect it would have been much closer to the AT specs-wise, and built around a 68000.
