The nucleus of a hydrogen atom is a proton of mass 1.67 × 10–27 kg which has only about one-fourth of the mass of an alpha particle (6.64 × 10–27 kg). Alpha particle is more massive and it won't bounce back in even a head-on collision with a proton. It is like a bowling ball colliding with a ping-pong ball at rest. Thus, there would be no large angle scattering in this case.
In Rutherford's experiment, by contrast, there was large-angle scattering because a gold nucleus is more massive than an alpha-particle. The analogy is there is a ping-pong ball hitting a bowling ball at rest.
