In San Antonio. We have had a lot of rain after a long drought. Not sure if that is a factor. Some of these developers cut corners. I have worked around some of the job sites and have seen things that don't look right but heck, if you cover it with enough dirt... I was under the impression that all of these slopes greater than 4 ft. needed to be engineered. That "retaining" wall looked a little shoddy for holding back that much dirt but was supposedly engineered. Another issue I see, a number of developers clear all the trees out under "ag use" while the cows are still grazing and before the property becomes a development. But that's another loophole the greedy developers use to rape the land. No roots to hold the soil. Poor soils, high clay content, no place for water to go..disaster.
Not saying this was one of those cases but it's common here and a lot of that dirt looks like fill.