What were the historical circumstances?
The Civil War.
After Buchanan botched the whole Utah Territory situation following the Mountain Meadows Massacre, Lincoln's focus was "first things first" - he did not want to create a new Confederate ally and a third front in the Civil War.
After the Civil War, the US government put an end to the illegal LDS theocracy in Utah.
Lincoln was dead after the Civil War..
Abe's famous response was to compare the polygamous Mormons to a large tree that had fallen in a field. Too tough to chop and too large to move, you would plow around it for a while and let it rot.
After the Civil War, the US government put an end to the illegal LDS theocracy in Utah.
About 40 years passed after the end of the Civil War before the Feds were able to convince the LDS Church (through brute force) to officially end polygamy.