Bike Anti-Porn - When Things Go Wrong

Metallurgists can have their say, but to me it looks like the front member had a fatigue crack all the way through, or very nearly, before the rear member gave way under an abnormal load, albeit a loading which should have been no problem to an intact post. The combination of manufacturing process and shaping is asking for such fatigue failure. It would be churlish to blame Prolly for not checking for cracks before riding, because none of us does.

There doesn't seem to be evidence of creep but of poor structural quality on the front member (ha! Member...) which means the rear member was having to take on more load than it was designed for causing total failure.