This still leaves the mystery of why the pilots did not change course and avoid the storm rather than flying straight through it. From everything I've read, that's a major no-no.
Agreed. It has been covered in a previous post of mine with a video where satellite data shows a severe storm with little water; Having little water may have prevent it from being in the A330 radar. Satellite info shows that whomever flying that path would find themselves inside a terrible storm for 150 klms (12 minutes) and higher than usual, up to 15 klms high with 100/150 klms vertical winds, without any previous notice.
In the dark there were but the outside clouds, which were completely eventless. Inside it was the severe storm, unseen in the evening. If you can please watch the video, though spoken in portuguese.