Most simulations generate multiple moonlets and streams that then fall into Earth, merge into the moon or escape (e.g. like this or this).
The initial orbit tends to be close to the Earth. This means that gravitational interactions will will be strong, making it hard for there to remain multiple moons since they will tend to destabilize each other's orbits. Simulations have shown that Earth at most can keep three moon-sized moons, and that requires careful arrangement so their Hill spheres do not overlap and they do not get into the wrong orbital resonances. The moon's Hill sphere has a radius of 60,000 kilometres, so its early very near-Earth orbit after the impact would have interfered with anything else orbiting nearby. Had it been lighter maybe extra (small) moons might have made it.