An admission to start with: I've never flown a twin prop, so the following is just my speculation.
The clue is the relatively large number of mayday's that were issued before the impact. XYTG's view I feel is very close to the money.
Perhaps during the take-off run the pilot realised the rudder trim was set incorrectly. Perhaps at the time of realisation of this he was committed to rotate. Perhaps he was well aware that there was an upper airspeed limit under this trim configuration so he reduced power. Perhaps he got the power reduction change wrong during the stressful circumstances and overdid it with an already overweight aircraft. Perhaps he gave it the welly when he realised his mistake but it was too late as the plane started descending. Perhaps he realised that the situation was no longer recoverable and issued as many mayday calls as he could before impact.
Purely my speculation.