Final answer:
Robert Moses aimed to extend 5th Avenue through Washington Square Park to align with the City Beautiful movement's urban development goals, particularly to improve traffic flow in New York City.
Step-by-step explanation:
Robert Moses sought to extend 5th Avenue through Washington Square Park as part of his vision for New York City's urban development, which was influenced by the City Beautiful movement pioneered by designers like Olmsted and Burnham. The movement promoted creating larger park areas within cities, building wider boulevards to alleviate traffic congestion, and developing suburbs to reduce city congestion. Though not directly mentioned in the provided references, Moses' plans often sought to connect different parts of the city and manage traffic, and extending 5th Avenue might have been perceived by him as a way to improve traffic flow in a rapidly modernizing New York City.