So when a star collapses or collides with another star and the force is so strong that the only place for the force to go is inward is what creates a black hole. There's theories that the supermassive blackhole in the center of the Milky Way was formed by 2 stars colliding and creating a strong enough implosion to create Sagittarius A*. And there are more reports saying that the black hole became exponentially active about 200 years ago...