A misremembering of history on his part. It was universally reported - at the time - by both northern and southern papers - that VA joined the CSA in spirit on receipt of word that fighting had broken out. People danced in the street in joyous relief that the decision had finally been made.
That was on April 12. The Convention reconvened on the 13th to reconsider secession. Lincoln issued his call for troops on the 15th, which was then used as the pretext for secession. But VA made its decision on the 12th.
The people of the South had gotten tired of the sectional domineering, hectoring spirit of the North, ... and determined to sever the bonds that bound them together; Peacefully if they could, forcefully if they must
Thanks for the quote. To restate it, southerners had, quite humanly, become sick and disgusted of being told the institution on which their way of life was based was evil.
The only problem being that it WAS.
IOW, there was no horrible oppression justifying secession. They seceded because (some) northerners said mean things about them and hurt their feelings.
700k+ dead men later, I hope it was worth it.
I'm pretty sure that Big Cotton was motivated by money and power. They already had the Dred Scott decision, the Fugitive Slave Act, and Union politicians willing to make great compromises and concessions in order to avoid war. None of it was enough for the Slave Power because they figured they'd grow much faster and be much wealthier if they seceded.