a) Willie Horton wasn't in the 1960's it was in 1988, Republicans never stopped using hot button issues like crime welfare and affirmative action as racial wedge issues. What did happen was that starting under Democrat Bill Clinton crime dropped to historic lows and had welfare reform, as a result Republicans couldn't be as blatant. The Southern strategy was in full effect until the mid 90's, Republicans are constantly using imaginary voter fraud as a way to disenfranchise black voters and other Democratic voting groups so no this is not all ancient history genius. To this day Democratic Presidents have consistently outperformed Republican Presidents on the economy, again not ancient history genius.
b) people would rather succeed on merit than continually be told that they’re inferior? The glue that holds American conservatism in the 21st century is a sense of perpetual victimhood. Again Trumper in 2020 got about 12% of the black vote which is about average for a post 1964 Republican running against a non Obama Democrat.
c) Drug epidemics and the war on drugs, the loss of good paying jobs especially collapse of heavy manufacturing are the primary reasons for the damage to the nuclear family, not the "welfare state". Btw the US has the stingiest "welfare state" in the western world in case you didn't know.