Given the limited information available the only known is that it appears someone made a bad decision. What's not known is who and one should not presume to know. Perhaps it was the Marines and they didn't account for the environmental effects of their decision. Or as suggested they did a proper site survey but didn't adequately understand the changing environment. It wouldn’t be the first time a site survey was done weeks to months in advanced, especially for a high profile event at such a distance from home. Perhaps the operational and security requirements overrode the environmental effects and the host country or higher hq choose the LZ and the Marines had no say in the LZ selection. So quite possibly they landed where they were told despite their misgivings. This also would not be a first. Unless one knows the who and the why perhaps one should refrain from drawing conclusions?