What could go wrong?
Actually, I have flown a Cessna with similar engine /prop combination, and taking off at full gross, climbing at best angle, I reached 10,000 feet in 12 minutes. The ROC at 10,000 was 700 FPM. Venturing into a rising valley was not in my choices, but climbing along the side of a high mountain was comfortable. I did stay well away.
The only reason that I only took that bird no higher than 14,000 was lack of oxygen .
Sad that they made a mistake that turned a fine sightseeing trip into a fatal crash. Determining just what that mistake was will be a challenge. Wind produces a lot of turbulence, and they may have been tumbled to an unusual attitude, and failed to make a suitable recovery.
Sad outcome for their families.