Sean Charles' last attempt at St Kilda was torpedoed by his missus (and hence children) not moving down from Swan Hill, from what I heard. She simply didn't want to leave and he didn't want to be away from her and his children.
There are probably many different reasons why a bloke with all the talent doesn't make it. Injuries and attitude play a big part, but there are many who need a strong support group around them. If your family isn't standing by you, it's pretty hard to push yourself to the level of effort required.
BTW, this is only hearsay, and probably very unfair to Sean's missus.