Disclaimer: I am a lay man and a physics enthusiast, no more. My thought is that the initial inflationary event of the Big Bang was far more powerful than early gravity’s ability to counteract it, maybe even on the order of the nuclear forces. I’d speculate that the “pits” (“low pressure systems” if we analogize to storms) would have formed in this period. Once expansion slowed, maybe even just a few seconds in, the conditions might have been conducive for the pits to collapse into black holes.