I think the charges against management may also be part of the reason for the local problems. If management is in place, the plant can go out and get other laborers. With management under indictment, maybe unable to work everyday, etc. I bet there’s no one at the helm just now and everything is going to hell in a handbasket.
Run Postville, IA through Wikipedia. You’ll see the kosher meat processing plant was started by a group of Hasidic Jews from New York. A number of managers have been indicted not only for employing illegals but for child labor violations.
There was another meat processing plant at one time, but it burned down in 2003, then rebuilt elsewhere. There’s also a plastics factory in town.
There seems to be a fairly high number of single person households (IMO). I’d say they were there because of work and for no other reason. Without the work, those who were legal likely moved on.