Yeah… no. The “switch” did not happen as you claimed. The Republican Party became more conservative, and the Democratic Party more big government over decades. Voters slowly moved over decades for political motivations, economic motivations, and the like.

What did not happen is that all the racists decided to leave their racist party in the 60’s and the republicans, after signing the civil rights acts, decided “hey let’s all become racists now”. That is pure propaganda from the Democratic Party to hide their shameful past of which they have never apologized or made amends.

The history of the movements of the two political parties is much more sophisticated than you state. But whatever helps you sleep at night.