It was a C-130A. That means it was almost 50 years old.
I've seen the crash footage a few more times. It appears both wings broke at the same time. That leads me to believe the wings were overstressed, especially if there was metal fatique or corrosion. According to news reports this morning, the plane was repaired 4 years ago for cracked wings.
C-130s were designed to take a lot of abuse. The military has ridden them hard and put them away wet for decades. That kind of treatment is hard on a plane.