Okay, so if I understand correctly, this is what most cosmologists think:
1. The Big Bang happened. Why is unknown. All matter and energy came into existence at once, contained within a spacetime singularity.
2. In the first teeny tiny fraction of a second in the history of the universe, the (currently undetected) inflaton field expanded the universe to a relatively humongous size faster than the speed of light.
3. Having done its work to homogenize the universe, the inflaton effect stopped almost as soon as it had begun, from our perspective.
4. Dark energy (nobody really knows what that is either) became the primary driving force of spacetime expansion. It was slow at first, but a few billion years after the Big Bang, it started to accelerate the expansion.
So not one, but two completely unknown universal forces/fields are needed to explain why the mass and energy is distributed in an isotropic fashion even while the universe is expanding faster and faster. Uh huh. We could also summarize this as: even today nobody really has any accurate knowledge about the large scale nature of the universe, and physicists are making it up as they go.