Its hard not to speculate that this was weather.A few posts have given some good insight and they need repeating:
a)Never ever try to outclimb a cell
b)Speed margin is critical-hence choice of level
c)Interpretation of wx radar is an art and surprisingly over-looked in training
d)Once in it,enage cws,disengage AT,set turb N1 and fly attitude only
Pay-to-fly crews are common in Asia(no inference here to Air Asia or this crew).However,there are many airlines flying today with FO's neither trained nor allowed to takeoff and land,never mind interpret a wx radar screen and formulate a plan of action to avoid multiple cells.Wouldnt have been a dry cell here so either they didnt know how to use or interpret the wx radar or if they did,their avoidance action was insufficient.
All the Asian airlines(and many others also) use this pay-to-fly or fly free cadet system and its alarming.Ive seen a pilot try to follow the magenta line right into a storm that would tear the plane apart.And they dont land or takeoff yet theyre signed off(ie.theres no safety pilot which begs the question..what if the Captain keels over?).Ive watched in the sim where the pilot cant handle a simple V1 cut yet is always signed off.And these same guys are upgraded to left seat once they get the 3000 hours,all of it on autopilot.Only a while back,we saw the embarassing and sad crash of a 777 at KSFO simply because there was no electronic glideslope and they couldnt fly.We werent allowed to say anything because it wasnt pc or because it was racist.But these accidents cost lives and something must be said.
There is no substitute for airmanship and two experienced pilots upfront who have the healthiest respect for ITCZ weather.They steer well clear and they dont wait for ATC either(very often VHF will be temporarily lost due static and some guys want to keep the magenta line until they get clearance).