We have no idea how gigantic the star might have been in another dimension that collapsed and created our Big Bang, but that's my theory, as well. It's called a 'white hole'. Gravity would not have pulled everything back immediately because gravity spreads out into 9 dimensions, not just three. Terribly, terribly weak, compared to the other three forces.
When a star collapses to form a supermassive black hole, the fabric separating our three dimensions from others is torn and the material is filling up the 'space', maybe a millimeter away from us, yet undetectable, except for the effects of its gravity.
I predict if we use gravitational lensing to determine sizes of dark matter clumps around our galaxies, then we will see that, as the black hole swallows material, the 'surrounding' dark matter clumps will grow. The dark matter scaffolding wasn't already there to create galaxies, but, rather, the 'scaffolding' is being created by dark matter, the gravity of which is maintaining stars in orbits around the black hole.
Remember the mysterious light that appeared in the heavens light years away that slowly grew, before shrinking and disappearing? That was a star collapsing from another dimension into ours, spilling its star stuff into our Universe.
I have a high school education, so blast away.