How Does Space Expansion Change the Shape of the Universe?

Once space expanded that fast, it just basically all that energy went away. But the energy doesn't go away. It just turns into inflaton particles. Why don't the particles cause inflation though? Because those particles are now mass and energy which has a different effect on the shape of the universe. You only get that kind of rapid inflation when you have high potential energy,. not when you have a lot of massr mass itself doesn't cause accelerated expansion of the universe; Only potential energy does that.