Maybe they started out faster than light, hit the edge of the universe, and got bounced back like a reflection wave.
The 4 types of wave interactions ways that waves may interact with matter are reflection, refraction, diffraction, and interference. Maybe Neutrinos interact with each other in an interference pattern that knocks them down to sublight speed.
The 24 neutrinos detected from the 1987a Supernova got here the same time the light did. The gravity waves from a neutron star collision also arrived the same time light did. It appears the Universe is composed of different particles where their vibrations always move at the speed of light. This is why nothing can move faster than light because nothing can move faster than the vibration of which it is composed.