I agree with tribe in that winning helps keep players, but there's alot of factors in play. Actually in conference play over a 4 year period the programs with the most wins and best conference finishes have been :
Loyola 48 wins
Illinois State 41 wins
SIU 40 wins
UNI 39 wins
Bradley 36 wins
Drake 35 wins
MSU 33
Indiana St 31
UE brought up the rear and Valpo only had 3 years.
Of course Bradley won the last two tourneys which helps. Drake had multiple coaching changes, but has had a history for some time of losing top players . Indiana State really hasn't lost many as I recall, and actually until the year in between Marty and Walter UE hadn't lost much. Lusk lost a number of quality players and of course Ford has had alot of player movement though I can't say he's lost any real studs , Church being the most glaring last year. But coaching changes probably effect losses as much as anything.