  Galactic rotation curves exhibit diverse behavior in the inner regions, while
obeying an organizing principle, i.e., they can be approximately described by a
radial acceleration relation or the Modified Newtonian Dynamics phenomenology.
We analyze the rotation curve data from the SPARC sample, and explicitly
demonstrate that both the diversity and uniformity are naturally reproduced in
a hierarchical structure formation model with the addition of dark matter
self-interactions. The required concentrations of the dark matter halos are
fully consistent with the concentration-mass relation predicted by the Planck
cosmological model. The inferred stellar mass-to-light ($3.6 \mu m$) ratios
scatter around $0.5 M_\odot/L_\odot$, as expected from population synthesis
models, leading to a tight radial acceleration relation and baryonic
Tully-Fisher relation. The inferred stellar-halo mass relation is consistent
with the expectations from abundance matching. These results indicate that the
inner dark matter halos of galaxies are thermalized due to the
self-interactions of dark matter particles.
