What came before it was the Big Crunch. The always existing energy that went bang, went crunch before the bang.
"It was shown many decades ago by the theoretical physicist Richard C. Tolman that in such a bouncing universe the cycles grow longer and longer (because of the increase of entropy). This means that they were shorter and shorter the farther one looks back into the past, and in such a way that the total duration of all past cycles added together was finite. That is, even in the bouncing universe scenario the universe had a beginning. Second, the entropy of the universe increases with each cycle, and from the amount entropy that exists in the present cycle one can conclude that the number of past cycles was finite. Third, it is highly doubtful that a collapsing universe would bounce rather than simply ending in a Crunch. And fourth,
it was discovered in 1998 that the expansion of the universe is currently speeding up (the scientists who discovered this were awarded the Nobel Prize in physics for 2011), so that it is doubtful that the expansion will reverse and lead to a collapse at all."
Stephen M. Barr, professor of theoretical particle physics at the University of Delaware
BTW, I have been lying in wait of you bringing up the acceleration of matter away from us at the farthest extremes of the universe, so thank you.
But if entropy was the ruling factor, the matter of the universe farthest from us would be slowing down!!!!! So as far as the universe is concerned the SLoT is meaningless!!! Remember Hawking pointing out that in the universe the SLoT is the only Law that can violate itself when entropy laden matter enters a black hole. I posted that earlier in this thread.
Accelerating motion means MORE kinetic energy, not less. So what is causing the acceleration? There are several thoughts on that, but it could easily be the pull of the supermassive universal black hole of the big crunch. The singularity of the big crunch would be the same singularity of the big bang where for a single unstable moment the universe of already existing energy is neither expanding or contracting, like the ball tossed in the air, that I earlier described, that at its apex for a single unstable moment is neither rising nor falling and hits the ground with the exact same force that it was tossed in the air.