This is an opinion extracted from a captain of Iberia who flies A346 usually routing EZE-MAD.
pilotosdeiberia.com :: Ver tema - Pedida contacto radar Airbus 330 de Air France en Brasil
The A330/340 hash two independent radar systems that share the plate of the antenna, so the failure of one does not imply a loss of another. The radome is partly protected by metal bands that are just to attract lightnings.
Moreover, in the latest versions of both A340 radar can operate simultaneously and independently, each sweeping a different portion of space in AUTO TILT.
Radar failure is unlikely. Also, if you have the misfortune of having a radar failure at night you turn back as close as possible and go back from where you came or by where you know for sure that there are no clouds, you can optionally launch fuel to climb and evade CB, but that does not guarantee you will not hit any of the great CB, or you can ask for help to other aircrafts and follow them visually or with the TCAS. Anything but get deeper into the unknown.
The plane may have entered the storm because they didnīt see it, and I think the radar worked well.
The options for this are two. Or both drivers had their eyes closed, something unlikely and almost suicidal to cross the ITCZ, or otherwise information of Wx did not appear on screen, which is more logical and normal to say, because it happened to me several times.