Dark matter virtual objects hypothesis I've hypothesized for many years in my head that dark matter are the gravitational after effects of objects that have exploded. My understanding of physics is that when an object explodes, its center of mass remains in the same location. If that's the case, it seems that the gravity of that center of mass could remain. What observations or theories are there that counteract this hypothesis?
There are (at least) a couple of problems with your hypothesis.

The first problem is that dark matter is just that - dark, in other words it emits no light that we can detect. The exploded remnants of stars are not dark at all. Indeed the winds and superwinds associated with exploding stars are often extremely hot and luminous in the UV and X-ray region. Even when these winds have slowed and cooled, they will then form warm dust (because they are enriched in heavy elements) that is then detectable in the infrared part of the spectrum.

The second problem is that we know that the majority of dark matter is not just non-luminous "normal" matter. Estimates of the cosmic abundances of helium, deuterium and lithium produced in the big bang are sensitive to the overall density of this "normal" matter. These estimates tell us that only about 20% of the gravitating matter that appears to be required to explain the dynamics of the universe, the dynamics of galaxy clusters and the dynamics of galaxies, can be in the form of "normal" matter. But the atoms and particles released from an exploding star are just part of this "normal" matter budget - they have already been accounted for and so contribute nothing to solving this second dark matter problem.