A pilot flying any type a/c knows he must avoid problems, simply because some problems he might not be able to solve. One of these problems is weather. A pilot is a "problem avoider". And he can do this with only a knob turn.
As I understand, AF447's captain chose to not deviate from weather. He knew ITCZ was very active that night, but chose to straight cross it anyway. Was the flight running late? Strong headwind?
We will never know why he chose not to deviate, but this bad judgment together wiht bad timing on deciding to take his rest, led him to a huge problem. Iced pitots, UAS, autopilot disconnect, a/c descending stalled inside a Cb. When the captain made it back to the cockpit, he was presented with a huge, yet avoidable problem.
A simple knob turn, deviate and then go to sleep.