Fun scifi hypothesis - the only stars that don't go supernova as a part of collapse into a black hole are ones that are engineered to do so by the locals.
This makes sense.
We'd be seeing a lot more supernovas in the night sky if all/most stars had to go through one.
Fun scifi hypothesis - the only stars that don't go supernova as a part of collapse into a black hole are ones that are engineered to do so by the locals.