I believe if it's so dense that light can't escape then the gravitational force pulling everything to the center is so strong that everything is crushed into an infinitely small single point, and it's like a feedback loop where the more stuff that gets sucked in adds to the density and thus the strength of it's gravitational pull which means it can crush more into the singularity. I don't think there is any physical globe like object, no growing buildup of physical material. The "size" appears to increase because as it gains more mass it's able to pull light in from further away.

Not an expert but that's my basic understanding as a layman.