At any given time, the radius of the universe was greater than the Schwarzschild radius. Otherwise, the universe would have collapsed into a black hole. The Schwarzschild radius can only be zero if and only if the universe has no mass and no energy. Since the mass/energy of the universe was never zero, its Schwarzschild radius had to be greater than zero, and the radius of the universe, being greater at all times than its Schwarschild radius, could have never been zero. Therefore, the universe was never a singularity.