Structural failure - what, why, and how likely?

[Nurse2Pilot]

So aside from exceeding the flight envelope and corrosion, it seems like a little bit of luck as well? I've done a little reading on the incident mentioned and it seems like the aircraft wasn't stressed past the flight envelope, wasn't particularly neglected (article mentions just passing annual inspection 2 weeks prior), yet still suffered this failure. So just bad luck that despite all the measures in place, this failure still occurred?

Article referenced:
NTSB: Wing of plane in deadly ERAU crash showed fractures, metal fatigue - News - Daytona Beach News-Journal Online - Daytona Beach, FL