Well, I was answering the question as asked.
Answers to your follow up questions.
1) How is the speed of light determined? It’s not determined by anything. The speed of light is a constant of physics, just like any other physics constant. Note, though, that the speed of light will change depending on the medium that light is moving through.
2) Is it the difference between massive and massless particle? Is what the difference? Particles without mass (photons, and presumably gravitons) can travel at the speed of light because they have no mass. Particles with mass cannot because it would necessitate a divide by zero in the Lorentz Contraction, and you can’t divide by zero. In order to accelerate a particle with mass to the speed of light it would require infinite energy and its relativistic mass would go to infinity. It would also shrink to zero length in the direction of travel.
3) Higgs field stuff? No, I don’t think so. Higgs field is what gives mass to particles. Since photons have no mass, they do not interact with the Higgs field.