It doesn’t necessarily switch anything off or collapse - it’s possible for a star of the right mass and density to simply end up with a core that is held up only by degeneracy pressure, and the core slowly shrinks as it cools until it lies within its schwarzschild radius, and the rest of the star is either quietly consumed by this relatively slow process, or just escapes as though nothing much happened. Which from the outside looks like the star just turning off.

It cannot just escape without a push as the gravity is still the same?