In this photo, you can see loose bricks on the ground. this is evidence that a support post has collapsed completely or has shed bricks. As this occurred, the girder above sags.
When the girder sags, so does the floor above it. This occurs most often in older homes, ones built prior to the 1970s, before building codes drilled down on spacing. Most of the crawlspaces in Madisonville were constructed in the 1940s and 1950s, which means that they are prone to the spacing and sagging problems.