Why did the supreme court not support Roosevelt and his New Deal?
The Supreme Court had no opinion regarding Roosevelt's "New Deal."
The US Supreme Judicial Court can only rule on cases which are brought before it. There was a fear that the very conservative court would undo Roosevelt's landmark creations, the National Recovery Act, the Rural Electrification Act, etc.
The court did rule the Farm Recovery Act to be unconstitutional in 1935 and Democrats feared that that was just the beginning. FDR felt that a Constitutional Amendment was needed to assure his plan's success. But Justice Louis Brandeis pointed out to FDR that there was a much easier way. He noted that most of the justices were well over 70 years of age and would soon be retiring. FDR could simply tip the balance in his favor by appointing justices who would view his programs favorable, which is just what he did.