A guess: The Big Bang resulted in lots of pieces some of which were black holes, of a wide variety of masses. In particular, the black holes of billions of so

A guess: The Big Bang resulted in lots of pieces some of which were black holes, of a wide variety of masses. In particular, the black holes of billions of solar masses weren't formed from collapsing stars and didn't grow to that size by accumulation but were born that size. And for dark matter, that's from many black holes of tiny masses.