Urban Renewal Puns

Urban Renewal has (rightfully imo) garnered a reputation for being an overall disaster for many of the United States cities, especially cities like Detroit and Boston, with neighborhoods bulldozed in favor of highways, leading to economic immerisation and displaced residents for the cities. My question is, the way urban renewal was carried seems to have been so obviously destructive on the cities that it borders of actively malicious. Did the Federal planners genuinely think that they were helping the cities in question economically recover? Was the general idea that the cities were things of the past and everyone would soon live in the suburbs? Or was there another step of urban renewal besides highway building that was supposed to occur that never happened?

Having read through the process, it just seems bizarre that anyone who interfaced with city leadership and residents would think that building highways in such numbers was the path forward.

Usually urban renewal entails replacing low- and midrise buildings by highrises. Are there examples anywhere in the world of the reverse process, in which a street or neighborhood of highrises was replaced by mid- and lowrises? I'm especially interested in places where this process was driven by an intentional policy by the local municipality.