I leap to the conclusion Lincoln and his auxiliaries did not have the votes to peacefully pass the amendment it is sometimes claimed he wanted.
What Lincoln needed to “free the slaves” was war.
But first he would need a pretext for war. Which his navy found in the Gulf of Tonkin Incident. I meant to say, the Fort Sumter Incident.
You leap to a lot of things. But Lincoln and the Republicans were not fools. Their goal prior to the rebellion was to keep slavery penned into states where it already existed and let it wither on the vine.
What Lincoln needed to free the slaves was war.
If Lincoln fought the war to "free the slaves" then who went to war to "keep the slaves"?