The wall is there to prevent an overrunning aircraft from ramming into whatever’s behind the wall. It’s obviously not meant to stop a heavy jet at that speed, but for a smaller or slower aircraft, it could mean the difference between arresting the plane as softly as possible under the circumstances, and crashing the airplane anyways into trees, the localizer antennas, or public roads with cars and people on them, in a place that airport rescue and firefighters can’t easily reach.

I was completely incorrect about that specific airport. The mound is part of the localizer antenna, which was not visible on the video. More: https://www.youtube.com/watch?v=BzmptA6s-1g