Why is the ending scene appropriate to the younger's family and to mama in particular

Mama was right all along about the liquor store being a poor misguided investment. Walter learns that he has been scammed out of his father's insurance money. No money has been put away for Beneatha's medical school: he has invested all of the $6,500 Lena gave him in the store. Walter, in a moment of despair, cries out, "THAT MONEY IS MADE OUT OF MY FATHER'S FLESH." Walter must now tell his family the news. Upon learning of her brother's deception, Beneatha cries out in rage. Mama is devastated, remembering how her husband worked himself to his death. The scene closes with Lena looking to heaven for strength. The younger family is always oppressed whether it is by white people or even black people.