That is a fact of human nature that is not so changeable. Jerusalem was conquered, it is often asserted, but the crusader kingdom was short-lived. It may seem so from our own day, but it is not so. Jerusalem remained in crusader hands for 88 years, and the kingdom lasted in Palestine for 192 years. By any measure of human institutions, that is a long time.
Many countries today have shorter histories.
The other goal of the crusades was the defense of the Christian East, and many believe that they failed most dramatically at this. It is certainly true that the crusades did not do much for mutual understanding. The sack of Constantinople by the Fourth Crusade in 1204 closed an iron door between the Catholic West and Orthodox East. So great was the hatred engendered by this event that even when the Byzantines faced the extinction of their state, they preferred Turkish conquest to union with the pope in Rome. We cannot say with certainty, as some do, that the crusades actually shortened the life of the Byzantine Empire.