The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The captain’s excessive left rudder pedal input during the takeoff ground roll, which caused a large heading deviation and a left roll upon rotation that resulted in the left wingtip striking the ground.
Also from the NTSB final report:
Further examination of the airplane determined that the left wing had a permanent upward deflection starting about midspan of the left wing, resulting in the left wingtip being about 6 inches higher than the right wingtip.