What hope is given to people in the tomb saying Arthur is the once king and king that will be?

The belief that Arthur is the once and future king offers a profound sense of hope to people, suggesting that he will return to unite and lead them in times of need. This idea embodies the hope for renewal and redemption, inspiring loyalty and courage among his followers. It serves as a reminder of the enduring nature of leadership and the possibility of a better future through the return of a just and noble ruler. Ultimately, it symbolizes the timeless hope for a hero who will restore peace and prosperity.