Except that an attack on the USA by the CSA hardly constituted oppression of the people of the South that would justify their secession.
There is a longstanding and untrue myth that the Upper South states, including VA, seceded in reaction to Lincoln’s call for militia to “suppress insurrection.”
In actual fact, the move shifted dramatically throughout the region as soon as the CSA fired that first shot, and secession was from that point inevitable. That the CSA fired the first shot didn’t make any difference in the Upper South, it was the outbreak of fighting itself that led them to spring to the assistance of their regional brethren.
OTOH, in the Border states and in the North, especially the Lower North, the CSA firing first made a huge difference in the public perception of the war.
Mood, not move.
I think you meant "mood", but this is the great mystery that nobody fully understands.
Before Fort Sumter (April 12-14), Unionists held power throughout the Upper South -- Virginia, North Carolina, Tennessee & Arkansas.
After Sumter, Unionists lost in every state, beginning in Virginia, and the question is: what happened?
I think the answer is, those Unionists did not so much voluntarily change their minds as they were intimidated and threatened into supporting secessionists -- specifically to prevent a coup in Virginia, that would overthrow the pro-Union government and potentially kill any unreconstructed Unionists.
In the Upper South, majority Unionists were cowed, intimidated, threatened and overthrown by large minorities of Secessionists.
But in Border States (Delaware, Maryland, Kentucky, Missouri), the Secessionist minorities were just too small to have that same effect, and so they refused to secede.