  The negatively charged boron vacancy ($\mathrm{V}_{\mathrm{B}}^-$) in
hexagonal boron nitride (hBN) has garnered significant attention among defects
in two-dimensional materials. This owes, in part, to its deterministic
generation, well-characterized atomic structure, and optical polarizability at
room temperature. We investigate the latter through extensive measurements
probing both the ground and excited state polarization dynamics. We develop a
semiclassical model based on these measurements that predicts a near-unity
degree of spin polarization, surpassing other solid-state spin defects under
ambient conditions. Building upon our model, we include the presence of nuclear
spin degrees of freedom adjacent to the $\mathrm{V}_{\mathrm{B}}^-$ and perform
a comprehensive set of Lindbladian numerics to investigate the
hyperfine-induced polarization of the nuclear spins. Our simulations predict a
number of important features that emerge as a function of magnetic field which
are borne out by experiment.
