Southampton were always going to struggle eventually. You can't keep losing your best players and progress. You might get lucky for a year or two but eventually it catches up with you.
The rest are struggling because they're so frightened of failure they can't do anything but employ has been managers. The managerial merry-go-round is slowly killing the established clubs. It's been always panic, panic, panic... get Moyes on the phone, or Big Sam, Hodgson, Pardew, Hughes, Pulis, Lambert etc etc. I'll never understand why more clubs don't give fresh, up and coming managers a try. People with fresh ideas, a different approach and positivity.