My explanation makes the prediction that if you performed a social-science experiment where people felt sufficiently close to the conflict to be personally involved, they would support the likely winner. This might involve making people very frightened and thus not pass ethics committee approval, though.

When I was in elementary school playing pickup basketball games, it seemed to me that people preferred to play on whichever team was stronger, which often resulted in wildly unbalanced teams. Perhaps this tendency could be studied?