The generation of relativistic electrons (REs) during tokamak disruptions remains a major challenge for the safe operation of future fusion devices. A promising mitigation strategy is benign termination, in which hydrogenic injections of specific quantities facilitate magnetohydrodynamic (MHD) instabilities that redistribute the RE beam heat load over a large wetted wall area, avoiding localized damage [1]. However, a key uncertainty is the role of plasma density, which must fall to recombination levels after injection. This has been commonly attributed to density scaling of ideal MHD timescales. Recent results instead show that the governing instabilities evolve on resistive timescales, and that benign and non-benign terminations are not distinguishable by growth rates alone [2]. To resolve this issue, we present a first-principles explanation of the recombination requirement for benign termination of relativistic electron beams in tokamaks. Kinetic modeling including neutrals shows that the injection of neutrals over a finite quantity window, together with recombination, increases bulk resistivity. Nonlinear MHD simulations using the JOREK code demonstrate that this preferentially amplifies edge tearing modes, producing a more stochastic edge magnetic field during RE deconfinement, resulting in a larger RE wetted area. We identify resistivity, not the free electron density, to govern access to benign termination. This provides a broadly applicable and experimentally consistent picture of the MHD mechanisms behind the benign scenario, critical to its extrapolation to next-step devices. [1] C. Paz-Soldan et al. 2021 Nucl. Fusion. [2] C. F. B. Zimmermann et al. 2026 Nucl. Fusion.