Takata
No-one can so far explain why switching at 0210 to ALT2, due to unreliable airspeed, would cause an immediate upset as none of the similar events ever caused one! After being switched to manual control, any manual imput could cause one in relation with other unknown factors (workload, weather, technical, etc.)
Perhaps this is stated backwards.
"Why would an upset cause unreliable airspeed indications??", might be a better question.
The answer is in the link below and subsequent discussion.
http://www.pprune.org/6210302-post2647.html
Note: With the discovery of the wreckage virtually under its 2010 position, the case for an immediate loss of control becomes stronger. The key question becomes how can it happen?