A schematic of the electron acceleration mechanism at the flare loop top. In a quasi-steady state (top right), the inward plasma flow (u_E) driven by slow shocks opposes the outward magnetic field gradient (∇B), resulting in betatron cooling. Conversely, in an unsteady, expanding loop top (bottom right), the outward plasma flow aligns with the magnetic field gradient, leading to positive betatron acceleration. This difference explains the stronger net energization in the unsteady snapshot analyzed here.