By computing the ground state difference density, we show that the cavity induces a redistribution of electron density to stabilize or destabilize the TS geometry depending on the cavity polarization direction. Cavity-induced stabilization occurs by shifting electron density from intramolecular π-bonding orbitals to intermolecular bonding orbitals. Destabilization occurs through the opposite mechanism where the intermolecular bonding orbitals donate their electron density to intramolecular π-bonding orbitals. Thus, our results have provided a chemically relevant description of the cavity-induced changes to the ground state chemistry and thus changes to the molecular orbital theory inside the cavity. We extended this exploration to an arbitrary cavity polarization vector which leads to critical polarization angles that maximize the endo-/exoselectivity of the reaction. Here, we show that the optimal selectivity for the ground state reaction, in terms of the cavity polarization direction, does not well-correspond to a simple chemically relevant direction but rather involves complicated interplay between the many permanent and transition dipole orientations of the reacting molecules. Overall, we show that maximum selectivity for the endo and exo isomers can be achieved with relative barrier energies approaching ∼5 and ∼10 k B T, respectively. In the absence of orientational ordering, we find that the endo isomer is preferred by ∼k B T even in a collection of randomly oriented molecules coupled to the cavity.