Most likely because of the majorly unreal intense gravitational fields due to how emensly dense it actually is, the mass of the object can no longer support the infalling gravitational force and it just goes *poof*, i think this could probably be because if the matter were turned into energy, that energy could not take up any space, yet hold emense power, enabling the bending of space and the huge increase in teh gravitational force. Hows that sound?

: Also there is no possibility of the Pauli principle being violated. The probability of two electrons being in the same place at the same time with the same energy and momentum is zero. So how does a BH ever form and still not violate the exclusion principle.