The movement of white people out of neighbourhoods with black people, and the use of redlining to concentrate a marginalized group within those neighbourhoods led to a disinvestment of both private and public capital in those neighbourhoods, creating and later perpetuating the cycle of poverty that leads people to turn to crime to survive. It does make sense for people with the means to leave a neighbourhood (from a personal safety standpoint) when it starts to have an increased crime problem but that is not what is being described here. Instead, the people left due to the racism that was prevalent in the mid-20th century, well before the rise in crime that resulted from their leaving.