The answer to this is easy: Wavelength.
LIGO observation GW170817 was a treasure trove of data being one of the greatest multi-messenger observations in history. But to this day there is a reluctance to acknowledge the vastly differential observation of different wavelengths of light.
Although attributed to a cooling trend, the fact is that blackbody radiative events will include all spectra, yet only the smallest wavelengths (gamma) arrived here very shortly after the gravity waves. Correlated infrared and radio were not observed at all for days or even weeks afterwards.
This strongly implies that time dilation (cause of observed gravity) is for some reason granular (particle based), and that a small enough wavelegth will "move between the raindrops" of ambient time dilation (gravity).
What no particle can escape is the bow wave of its own time dilation, which is why they do not exceed the approximate speed of light.
Neutrinos are among the highest energy, and therefore smallest wavelength, particles that we know to exist. This is the reason they have so little interaction with matter and why they exceed their theoretically computed velocity despite being massive.
This is contrasted with the long wavelengths of infrared and radio which is why they will be by far the last wavelengths to be observed in any deep space multi-messenger observation of an event despite having no mass.