Q: Vehicle stalls when ignited and now it will not turn on

The issue with our vehicle is that it stalled and trembled when stopped. It got to the point where it no longer turned on. We have already changed the fuel pump and the started from a previous problem. However the problem with stalling and trembling augmented in the last month. We believed this may have been the catalytic converter and were correct, the ceramic monolith honeycomb core was completely broken and there was raw fuel inside. Catalytic converter was broken for other reasons of which we don't know the causes. A friend of our suggests that it may have something to do with the engine control module or the coil springs or ignition coils along with the spark plugs. We would like to know if you have any insights on what may be occurring. Thank you.

My car has 180000 miles.
My car has an automatic transmission.