We investigate the effect of externally applied resonant magnetic perturbations (RMPs) on the pedestal collapse, using resistive reduced magnetohydrodynamic simulations. The RMP-mediated nonlinear interaction is shown to enhance the fluctuation level, leading to an increase of convective transport. Further, it also induces a broad coherence and strong energy transfer among poloidal and toroidal harmonics. The enhanced fluctuations, especially at lower (than the most unstable mode) toroidal mode number n, eventually increase the tearing-parity fluctuation distinctively at lower n through a series of tearing-parity generation mechanism. Consequently, RMPs are shown to expedite the magnetic field line stochastization process via the nonlinear energy transfer process.