If the crew failed to find the weather on radar that likely took them down, the first warning would likely be the sound of ice pellets hitting he aircraft.
Most of my tactical jet XC work (ancient history) was without available weather radar. The only operational restrictions applied from on high was, "do not fly into Weather Warning areas." As a result, we had the opportunity to fly into and through some otherwise interesting weather. Other than some spectacular St Elmo's fire, it was not that exciting.
For the meteorologists here, did conditions in the ITCZ on the airway that day equate to WW level storm intensity?
I'm betting that the weather is more likely to have interfered with the aircraft's sensors and thus precipitated this accident.