Why was the missuori compromise more successful at making people on bothb sides of the slavery issue happy than the compromise of 1850 or kansas nebraska act

in this part of the declaration it refers to the point when american people didn't recognize the british domain and   breaks the political bands with britain, they forced a respectful separation.

mankind was created and entitled equally with rights   which were life, freedom and the seeking for happiness.

i am confused, what is the question? i can you out if you put it into more depth.