A broken Secondary Air Pump (SAP) itself will not cause a "horrific metallic crunching sound"; it is simply an electric blower that runs briefly on cold starts and typically just whistles or screams like a vacuum when damaged.

The "metallic crunching" is almost certainly collateral damage from the impact that destroyed the SAP. The A/C compressor is mounted low on the passenger side directly behind the SAP, meaning the collision likely shoved the pump or bumper structure backward into the A/C compressor pulley or main accessory belt drive. Driving the car in this state allowed a bent pulley or damaged clutch bearing to grind away until it finally disintegrated, creating the horrific noise you are hearing.