Why did Lincoln deliberately downplay the slavery aspect of the Civil War?

He downplayed the slavery aspect because he would need to win the war first to enforce it

Explanation:

The slavery act (emancipation act) which was made by Abraham Lincoln in the 3rd year of the civil war that ensured that all slaves held in the confederate states would be freed after the war was over.

Lincoln downplayed the act so that it won't be seen as act of pity or an act to downplay the Military prowess of his military in winning the war and also he knew that to be able to enforce the act on the confederate states he has to first win the Civil war. Abraham Lincoln was the First American president after America gained its independence from the British.

Lincoln deliberately made his Emancipation Proclamation limited as he did not want to alienate slave holders in the Union or Confederacy. He also hoped that some slave states would voluntarily come back into the Union. A military victory was needed as Lincoln did not want the Proclamation to look like the last gasp of a failing government.