Ask a naive question, how can a black hole be compressed to such a large density?

The pressure of 1 comes from gravity. When the mass of a star is large enough, it can generate enough pressure to destroy the atomic structure. Human science and technology just can't reach this ability. Don't think human beings are awesome. Maybe one day the sun will blow out a cloud of ions and destroy all life on earth, just like playing.

Black holes are constantly absorbing foreign matter, and their energy and mass are also increasing. When its energy reaches a certain limit, it may eject something (similar to a volcano on the earth), or it may explode directly, and the ejected material will form a new celestial body.