Research shows that this is due to forgetting to take out the lifting eye from the crankshaft. When the one of the lifting eyes is still in place the first rotation of the crankshaft allows the rod to hit the eye-bolt, bending it around in a circular manner. Notice the perfectly round bend.
A few years ago one like this snapped the eye-bolt instead of bending the rod. The subsequent scraping of the rod with the sheared off bolt created enough heat that it created oil vapours in the crankcase, which eventually ignited killing 3 workers and blowing the exteriour panels off the HSD assembly hall. The $10M engine was also trashed.