What fundamental stellar state causes a core-collapse supernova to be triggered?

Answer

Exhaustion of nuclear fuel leading to inability to support gravity

A supernova marks the violent end of a star that has run out of nuclear fuel and can no longer support itself against the crushing force of its own gravity, causing the core to collapse rapidly.

What fundamental stellar state causes a core-collapse supernova to be triggered?
evolutionastronomystarsupernovaremnant