Circuit Testing failed (Reverse polarity and Buck-Converter)
TVS can fail in shorted mode, it is actually the preferred failure mode as it still protects the circuit against overvoltage.
TVS is (without additional components) usually not suitable to clamp sustained overvoltage. It is intended for clamping voltage spikes (short duration) If you check your datasheet, the 600 W applies to pulse only (it is actually more energy limit than power limit). Sustained power absolute maximum is 3 W only, with 30V drop it is 100 mA only.
It is well possible that your C2 capacitor failed as well. What is its voltage rating? Typical overvoltage failure mode of MLCCs is short circuit.