Why would a buck converter IC fail and blow up?
I suspect overvoltage on the chip, with a second possibility inductor saturation as @oldfart suggested in a comment.

Your supply bypass is an electrolytic capacitor, a little far from the chip and is a small electrolytic so it has a relatively high ESR (and, unfortunately, an ESR that will increase as the capacitor ages).

The input ripple current, in combination with stray inductance from wiring can lead to overvoltage on the chip input. I suggest testing it with a supply with long wires and test at the limits of the supply range. Put an oscilloscope on the power rails and see how big the spikes are. A ceramic 22&nbsp;µF capacitor with an electrolytic (e.g. 1000&nbsp;µF/25&nbsp;V 105&nbsp;°C) in parallel, if you have room, would be much better. Check that the "22&nbsp;µF" ceramic is over 10&nbsp;µF at the maximum operating voltage. It should be as close as practical to the chip. And, of course, it's best to follow the suggested layout practices in the datasheet as closely as practical.



Inductor saturation is a different issue- it would tend to occur at minimum supply voltage where the input current is maximum. You can test it by bypassing your undervoltage lockout and reducing the input well below the minimum normally expected. Symptoms would be excessive power dissipation in the chip.