Oddly enough, Lincoln did try to free the slaves in Delaware, just as he did in Washington, DC, through law, using compensated emancipation.
Turns out, the good citizens of Delaware & Kentucky chose not to accept compensation, preferring to wait until their slaves were freed by Constitutional Amendment, without compensation.
Marylanders, West Virginians & Missourians chose to free their slaves on their own, without waiting for a national Constitutional Amendment.
None of those Union slave-states chose rebellion to prevent emancipation.
Union leaders understood from Day One that states in rebellion were driven first to defend slavery, and that attacking their slavery was essential to destroying their rebellion -- so they did.
That's why, Virginia, it was indeed all about slavery.
Sounds like a misread of the teleprompter by the other affable Joe; Jen will need to circle back.
Otherwise, expect our beloved Brother Joe to once again heft the old burden - which has some controversial documentary support - that from the time of Lincoln's “house divided speech” the rail-splitter/nation-splitter had intentions to use the presidency and the military to violently overthrow constitutional slavery; because it was "all about freeing the slaves."