One other factor that might influence retention rates: the more selective a school, the more likely a student might be to stay even if they aren’t particularly happy there. That is, if you were admitted to one of the schools that admit very few students, there is a fair bit of psychological pressure to stay there (how can you give up this opportunity??!!!). At a less selective school, if it isn’t working out particularly well, there will be less pressure to stay.
Common theme is that freshman to sophomore retention rates seem to track the same schools that are favored for a variety of other reasons (difficult to gain admission, meets financial need, students are high achievers, generally from more affluent families, etc.).