Answer:
Mama's trust in Walter waned because of his poor judgement.
His role in the Younger family was affected negatively as the other family members rejected him.
Step-by-step explanation:
Walter was desperate to accept Mr. Lindner's offer of money so that his family, the Younger's family do not move into their own house. Walter was eager to accept this money which mama told him to reject. He became defiant and downhearted as a result of this. His sister Beneatha even said that he was no longer her brother. All of this made Walter feel worse.
However, when Mr. Lindner finally came with the money offer, Walter made the decision to reject the money and move with his family. This made his mother proud of him.