A 42-year-old Indian woman with known myasthenia gravis presents to the emergency department with acute respiratory distress and inability to swallow. She has not taken her medications for 3 days. Arterial blood gas shows pH 7.28, PaCO₂ 65 mmHg, HCO₃⁻ 28 mEq/L. Bedside spirometry reveals forced vital capacity (FVC) of 800 mL (baseline 2.5 L). She is immediately intubated and started on mechanical ventilation. Which mechanism best explains why anticholinesterase inhibitors (pyridostigmine) are effective in reversing her neuromuscular weakness?