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In this study, we employ ab initio density functional theory (DFT) calculations to elucidate the microscopic origin of the Jahn-Teller distortion suppression and magnetic moment quenching in LiNiO2 (LNO) during delithiation. Our results reveal that these effects arise not from changes in the Ni oxidation state but from an electronic charge redistribution between the eg and t2g orbitals derived from Ni-3d states. This internal electronic rearrangement, driven by strong hybridization between Ni-3d and O-2p orbitals, accounts for the inactivation of the Jahn-Teller distortion and the quenching of the magnetic moment at the NiO6 octahedra. The same mechanism also explains the shifts observed in the Ni and O K-edge X-ray absorption near-edge structure (XANES) spectra during delithiation. Our findings provide a new microscopic interpretation of the LNO redox process, highlighting the role of electron redistribution within the Ni-3d manifold as the true origin of its structural and magnetic transformations.