It seems to me that the universe must itself have begun as the collapse of matter into a black whole - that the initial singularity was that collapse. It must be, because all that mass together has an event horizon - it was (and still is) a black whole in the aggregate.

And so perhaps the "expansion" that resulted, was not so much an expansion, but is better seen as the collapse of dimensionality. That is, perhaps the Planck length got reset, to be relative to the space in which we exist - our black whole universe. Perhaps the expansion of the universe is just the contraction of our spatial dimensions.

And if my premise is true, then the initial structure of the universe would result partly from the way in which the initial collapse occurred - there would be a signature of that collapse; and perhaps some of that signature is conentrations of mass, which then became their own (early) black wholes within our universe.