Why did Southern Democrats push for Jim Crow's segregation laws?

"Our republican system was aimed at a homogenous people, while blacks continue to live with whites, they constitute a threat to national life, family life can also collapse and the rise of mixed-race bastards can one day challenge the supremacy of man. White." … -Lincoln

The whole south was racist. The laws of Jim Crow were bipartisan. The hard-core racists in the south thought that blacks were a subhuman species bearer of malevolence.
The equality of blacks did not appear as a political priority until the mid-fifties. The others changed their name to embrace him, the opposition came from the south and from the representatives. This is how the south became so red today.
Martin Luther King intervened in the Republican party during his life. In chapter 23 of his autobiography, King writes this about the 1964 Republican National Convention:

"The Republican Party adapted its appeal and program to racism, reaction and extremism, and all people of good will saw with alarm and concern the frantic wedding at the KKK Cow Palace with the radical right."

"In US politics, the strategy of the South was an electoral strategy of the Republican Party to increase political support among white voters in the South by appealing to racism against African Americans.[1][2][3]"
https: //en.wikipedia.org/wiki/Southern_s …

The Dixiecrats became representatives due to civil rights. Strom Thurmond is a symbol of the transition.

An imam of controversy during his senate career for nearly half a century, Thurmond switched sides due to his support for the conservatism of Republican presidential candidate Sen. Barry Goldwater.In the months before the change, he had "criticized the Democratic Administration." "… enactment of the Civil Rights Act",[2] while Goldwater "boasted of its opposition to the Civil Rights Act, and made it part of its platform."[3]"
https: //en.wikipedia.org/wiki/Strom_Thur …