Bungalow Colonies proliferated after WWII and the majority were Jewish, but NOT frum.
This was during the baby boom when small NYC apartments were overcrowded by young families with little space and no air conditioning.
My grandparents owned a bungalow colony near Loch Sheldrake and we often visited for a week in the summer in the 50s.
By the early 1960s most non-frum Jews no longer went to bungalow colonies, many had escaped crowded NYC apartments for a small suburban home with a patch a grass.
Also, in 1964, President Johnson singed the Civil Rights Act. Jews could not be legally kept out of beach and country clubs or hotels/resorts. There now were many choices for non-frum Jews to vacation. with the advent of cheap Jet travel the attraction of the Catskills died out for many.
Frum Jews took advantage of changing conditions and bought up failed bungalow colonies. Some became schools/Yeshivos. Others became condominiums/coops instead of profit making businesses.
BUT, the wife and kids still spend most of the time there without husband.father who still commutes from the city for Shabbos.
BTW, It’s not all about Brooklyn. My grandparents who owned the colony were from the Bronx, as were most of their renters.