Is it impossible for the rich to be saved? Not impossible, for God can deliver him from needing his riches, from revelling in them. Even if it is the will God that he should later return to them, God can make him one who is be detached from them, and puts them to good use for the kingdom of heaven.
But why are riches such an obstacle? Riches make us too big in our own eyes, and we believe in the eyes of others also. We are not willing to lose that imagined advantage. They become tied up with our sense of self-worth. We have too much baggage, too much self-importance. Riches also provide security. We trust in riches and possessions rather than trusting in the Lord. The rich young ruler was required by Christ to deal a fatal blow to his earthly security, and he could not do it. This was part of his repentance.