What led Harburg to write the song, "Brother, Can You Spare a Dime?"

The correct answer is the second sentence actually " the realization that the prosperity of the past was completely gone and very unlikely to return"

Harburg wanted to show that many people, including him, cannot comprehend how all these men who built the nation are now begging for money and can barely survive. The realization that America is falling apart is tragic for them.