Except by the time Bradley design was finalizing towards prototypes, the new category was already defined. It was never supposed to be just another APC, because

Except by the time Bradley design was finalizing towards prototypes, the new category was already defined. It was never supposed to be just another APC, because M113 was already known to be deficient, and the long and tortured process happened because Army didn't know the goal yet - and thus required exploratory work. And then BMP-1 kicked the anthill.