Infatuation or crush is fleeting. It is not a permanent emotion that one feels attached with someone. People change and that is the main reason why.
If the people smitten would not do something about their emotions, it would not last.
True love on the other hand tends to be permanent. Love has a deeper connotation, it is an assumed fact that deep emotional closeness has already been established--it is a selfless concern for the welfare of the beloved.
It can eventually lead to commitment, however, it still depends upon the willingness of both couple to how far would they go for the relationship.