It's usually not noticeable but with this amount of energy, the gravity due to energy does become important. The gravity during the collapse is due to both the actual mass of the stellar core and the energy released as it collapses. Back in 1796, it was already suggested something could be so massive and yet so small that the escape velocity would be greater than the speed of light. Einstein showed that space and time are actually tied together. Time is just a dimension, so we live in 4-dimensional spacetime.
Gravity is really just mass effecting spacetime .
A large mass with a small radius would create an infinitely deep depression , meaning anything that got too close would never get out. A black hole is hole in the Universe. Bigger mass, bigger event horizon. We have no way of knowing what happens to material that falls into a black hole, and can only measure the mass, angular momentum and electrical charge for ones in binary systems. No information can get out.