I’m a layman but I think I’ve understood this enough to repeat. The early universe is hypothesized to have been so uniform (gravity pulling in every direction) there was no net direction for anything to collapse to. Because the expansion was so quick, before the uniformity could be ruined due to quantum randomness, it expanded away from there being tons of or one giant black hole.

You also must remember the universe was always infinite (in this model). So for every particle there were particles in every direction from them, ie the universe not a point or point like because points have edges. It was (much much) denser, but still infinite and expanding from all regions.

That's a question that I always also asked myself, from my layman understanding space time expanded quicker than gravitational collapse