That is a point well taken but not all of the Missouri militia units marched against the Mormons once Governor Boggs issued his extermination order (that remained in effect until it was rescinded in 1976). Sterling Price did met with Joseph Smith, toured his capital at Far West and did not take part in the expedition that drove the Mormons from the state although his men did later guard Smith and his confederates in the Liberty Jail.

Missouri militia units remained the nucleus of the units that moved into the Kansas Territory repeatedly in the mid 1850s however.

I think the diference in why effort failed and the other suceeded was three fold: weapons, political support and deep financial pockets.

For better or worse the Mormons allowed themselves to be disarmed at least twice by local autorities some say three times while the neighboring Missourians never seemed to be forced to turn in their weapons.

Fighting against the spread of slavery was a much more appealing cause than taking up arms in defense of a religion whose leader claimed her spoke directly to God and that multiple wives was OK. Hence the LDS Church enjoyed no widespread support in the general American populace.

Third, the Mormons hocked everything they had to get to Missouri and had no financial reserves especially after their church bank in Kirkland, Ohio, failed. Whereas the Free Staters in Kansas enjoyed the backing of several wealthy New England tycoons who desperately wanted to free slaves in Kansas and Missouri while working Irsih women and children to the point of exhaustion in their factories back east. Interesting world isn't it. Scott