The major impetus for unification was the promise to build the subway. Manhattan had the money but needed the land, Brooklyn and Queens had land but not the wealth.

Once upon a time Flushing was hyper religious Quakers. When the NY & Flushing RR was built (today the Port Washington branch of LIRR), one of the anecdotes in its history was the moral outcry when they tried to run a single train per day on Sunday. They appointed actual fun police to make sure no rowdy drunkards would dare come to their town hoping to have a good time. What do they think this is, Brooklyn? LIC was literally built by and for the railroads. Before the tunnels into Manhattan (1906 IIRC), you would get off the LIRR (or other competing services which were later bought out) and switch to a ferry to cross the East river at Hunters Point. LIC was always de facto colonization by Manhattanites.