High mass stars can end up as neutron stars or black holes. Supernova remnants are very small. Therefore, they are difficult to see using visible wavelengths. Neutron stars tend to have rapid rotation and very strong magnetic fields . These conditions can result in an object called a pulsar.
Pulsars are very easy to detect with radio waves because of the rapid fluctuations.
A rapidly changing object is easier to detect than a stagnant object, much as a deer is more visible in the woods if it is moving. Black holes can only be detected by monitoring the behavior of matter as it falls into the event horizon. I supernova are one possible outcome of a low mass star death. A low mass star evolves into a white dwarf. If the white dwarf is singular, then it will simply cool to a black dwarf.