@Landflap
Faced with a wall of severe weather, why not turn back ? If that was not an option, why not divert to another airfield a wait it out ?
IF this was a 'weather related' event and if the crew flew this route on a regular basis, it's very likely that they had encountered similar weather conditions on many previous occasions.
After all, monstrous storms are fairly common in this area.
Maybe they just adopted their usual procedure for dealing with what they regarded as a routine situation, but on this occasion luck was just not with them...