Buck Converter dies unpredictably upon connecting power
This is due to inrush current. To get a good feel for what you are actually dealing with a simulation is always a good help! (LTspice is worth looking into) 



As you can in the simulation the capacitor takes in (approximately...) 20 A peak at 24 V. To limit a high rate of change in current, an inductor can be used. But this will induce voltage oscillations at the input. This is not completely avoidable but you should try and dampen them as much as possible. 

The simulation I did is NOT a complete solution. You should play with it to see what works. A TVS diode might help you out, but a proper input filter should be able to deal with the problem.

(also on page 10 of the datasheet, there is mention of some soft-start circuit with the EN(able)-pin which will alleviate things more.)