a cut from the attached Forbes article that explains why the comments were made...
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“Secretary Buttiegieg is absolutely correct,” Princeton University history professor Kevin Kruse told Forbes Monday. “The history of highway construction shows that race was a significant factor in the placement of new roadways in the 1950s and 1960s. New interstate highways weren’t built on a blank landscape. They had to be routed through existing neighborhoods, which were largely destroyed in the process of construction.”
Link: https://www.forbes.com/sites/jackbrewster/2021/04/12/republicans-mock-buttigieg-for-saying-highways-are-racist-but-heres-what-he-meant/?sh=6f2a65bc2cf5