Get a list of all democrats in office then highlight the ones who changed party. The number that switched were a small minority. Wikipedia lists less than 70 and most of those were state rather than federal.
Compared to the thousands of state and federal seats, it’s minimal.
So-called civil rights pioneers like Lyndon Johnson were raging racist who saw the civil rights act as cheap lip service to get black votes for decades to come.
You also forget that republicans were radically IN FAVOR of civil rights, but wanted the changes at the state level instead of the federal level.
As someone who has lived in the south (my family is not from the south), I’ll tell you that the Republicans were correct. The clan controlled the local counties (most important offices) and nobody would stop them from disappearing people or burning them out of their homes regardless of that the federal government said.
What changed was the people. Each generation has grown more tolerant. That finally broke the clan control and the millennial generation in the South is overwhelmingly not racist.
Unfortunately, the recent moves away from MLK-style equality to the radical Marxist-style equity (equity except for people who happen to be born white as they see it — very similar to Russian discrimination against children of formerly Middle/upper class people like engineers) seem to be pushing gen Z back toward racial supremacy (this seems true across the whole country).
https://en.wikipedia.org/wiki/List_of_party_switchers_in_the...
The most interesting question is why republicans and democrats supposedly swapped parties in the 1960s, but the black vote shifted in the 1930s. The answer seems pretty clear. Black unemployment was through the roof and the New Deal promised jobs, so they broke with the part of Lincoln because they were forced to. As things stabilized, there was a risk of them switching back and once again creating a Republican supermajority which is what spawned support for a federal civil rights act by the racist democrats.