We already know all about it:

>White flight or white exodus is the sudden or gradual large-scale migration of white people from areas becoming more racially or ethnoculturally diverse. Starting in the 1950s and 1960s, the terms became popular in the United States. They referred to the large-scale migration of people of various European ancestries from racially mixed urban regions to more racially homogeneous suburban or exurban regions. The term has more recently been applied to other migrations by whites, from older, inner suburbs to rural areas, as well as from the U.S. Northeast and Midwest to the milder climate in the Southeast and Southwest....
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>The business practices of redlining, mortgage discrimination, and racially restrictive covenants contributed to the overcrowding and physical deterioration of areas with large minority populations. Such conditions are considered to have contributed to the emigration of other populations. The limited facilities for banking and insurance, due to a perceived lack of profitability, and other social services, and extra fees meant to hedge against perceived profit issues, increased their cost to residents in predominantly non-white suburbs and city neighborhoods.

Lots of things, notable among them… racism