Johnson's 'conversion' to Civil Right crusader in 1964 came as a shock because many Northerners assumed that LBJ was a racist, due to his being from Texas. Prior to 1964, Johnson had managed to get the only major civil rights legislation since Reconstruction through the United States Senate, and had done so at risk to his own political base.
LBJ's stance on civil rights legislation isn't without some ambiguity; he did take a turn to the Right in his political stances upon reaching the Senate, and he went along with the Southern bloc on many issues. But, on a personal level, he appears to have always been a supporter of equal rights. This is the same man who, upon finding out that a local veteran would not be buried in a cemetary because of his race, lobbied to have him buried in Arlington National Cemetary, instead. Stories like that are not few and far between.
However, being a consumate politician, he often acted only when he could minimize the danger to his own aspirations, and if he saw some greater reward down the line. In many ways, Johnson was always a deeply conflicted man; torn between a desire to be viewed as hardnosed and practical, on one hand, yet possessing a strong romantic streak as well. When he could manage to fuse both of those two together, the man could move mountains.
I'm glad to see you did the reading.