Complex sentence: The party did not remain a lasting feature most probably because it had been so closely identified with the free silver movement which did not resonate with urban voters and ceased to become a major issue as the U.S came out of the recession of the 1890s.
Split into simpler sentences: The party did not remain a lasting feature most probably because it had been so closely identified with the free silver movement which was not meaningful for urban voters. Currency ceased to become a major issue as the U.S came out of the recession of the 1890s.