In that case, the big burst of energy became a ball of energy emerging into existing space. Energy emerging into space like that would have energy density. It would be natural for high pressure emerging energy to begin to expand in pre-existing space.
My reference to expanding space should have been made more clearly. I was talking about energy expanding in space; energy density expanding and as it expands the pressure is declining. As it declines it reaches the pressure where matter can form.
I see no reason why energy in space cannot expand faster than the speed of light, but if matter did not exist yet, even the energy I am suggesting that emerged from the big burst didn’t have to travel faster than light.
Even if it traveled at a turtles pace, time (at least as we use it to measure the age of the universe) did not start until matter formed. If the energy had expanded in space by 10^50 before matter formed then time did not start until the energy that occupies our universe was inflated sufficiently to make the causal connection without the need for any matter to travel faster than the speed of light, IMHO.