The Big Bang did not collapse into a giant black hole because the universe expanded too rapidly for gravity to pull it back together. In a black hole, the matter is so dense that its gravity prevents anything, even light, from escaping.

However, in the early universe, the matter was very spread out and had a relatively low density. This meant that the gravitational pull between particles was not strong enough to overcome the outward pressure of the expanding universe. As a result, the universe continued to expand and did not collapse into a black hole.