Cause of the WBTS

KY (like TN [Which, BTW, was the last state to secede from the Union & the first one to be readmitted back into the Union.]) was basically divided into three geographic areas (& still is).

East KY is very mountainous & thus was more conducive to very small farming on rather rocky soil. Hence, its agrarian economy (as well as its weather [very short growing period{s}]) would not support a "plantation-style" farming arrangement.

West KY (basically the lands to the west of I-65) tended to be much flatter than E KY, so it could manage a "plantation-style" farming much better. Also, its proximity to major rivers such as the Ohio River which pretty much forms its entire western border made it much easier to export cash crops (esp. cotton & to a much lesser extent tobacco) to markets in Europe and elsewhere.

What one has left in KY would be Central KY. It had a mixture of both E & W KY's economies.

This is one reason that even today (although to a much lesser extent today than it would be during the 19th century era) E KY would be considered "GOP territory" and W KY would be considered "Democrat" territory. Central KY was "up for grabs" by either of the two.

There was actually a secession movement in W KY to pull out of the Union and join the CSA (just like WVA did except their goal would be to join the Union [Which they did in 1863]).

Bowling Green KY (Where Salty's Corvettes are made!) was more-or-less the "capital" of W KY in those days. If one studies the campaigns of the occupying Union forces in TN, one will notice that some of them were directed to "discourage" W KY from seceding from the Union.

This is why the adage that "KY was the first state to join the CSA after the WBTS was over," was a fairly accurate assessment of what the Blue Grass State did in 1865 ff.