Flatbush,,Brooklyn in the 60s was basically Irish,Italian, German, and Jewish.It was and has always been Mom and Pop Stores, working class, and numerous Religions.
In the mid 70s to the mid-90s crime entered the area as the demographics changed. There is no correlation between the two.
Caribbeans entered the area. Matter of ffact the rezoning thhat started in 2010 did not improve the are, but an organization called The Community Action Project organized by PICO headed by Pierrre Francois Louis.