The appearance of the break seems to indicate that the failure may have originated at a crack that may have been there for some time. No doubt more will be learned once the safety board issues a report.
As the broken gear leg dug into the grass the aircraft "cart-wheeled" causing substantial damage to all four wings, and distorting the forward fuselage.
Let's be sure to learn from this and check this area carefully during inspections. Remember what has been learned about the flying/landing wire fittings too!
Thanks to Tom Muller for sharing this important information.
Update -
Jesus Ballerster points out that there a possibility that water can become trapped inside the gear legs and may lead to rusting. It is common practice to drill a hole in the gear leg to allow the water escaper like so:
Several updates were made to the landing gear system over the years. To see if you have the latest check the document "CASA landing gear modifications.doc" in the Jesus Ballester collection on the Downloads/documents page.
Thanks again to Jesus for providing this information.