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Aircraft are not meant to be downed by lightning... it happens frequently, they are designed for this. Lightning alone isn't enough.
AF447 sent 24 automated (ACARS) messages reporting AF ops about system failures. The first is an autopilot disengage, the second is the aircraft's flight control systems switching to ALT LAW. This basically means (if the AP wasn't disengaged by the crew) the aircraft's flight parameters were not manageable by the AP anymore (the control system could not guarantee the aircraft to fly in it's designed envelope), therefore it disengages itself.
Switching to ALT LAW means the pilots have more direct control of the aircraft's control surfaces. It's the middle one of 3 flight laws an Airbus has, each law referring to the amount of direct control vs. computer protection of overstress, etc. Switching to ALT LAW is (as I recall), again a sign that the crew need to react to regain the aircraft's normal flight. This reaction most probably cannot be enough if in full protection mode, therefore ALT enables a more drastic one.
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