It was finally swayed to join the Confederacy by only one thing and that was Lincoln's call for 75,000 troops, and his demanding that Arkansas send troops to fight against the Southern States. That is the one thing that united the people of Arkansas. They would not fight an offensive war against they sister states, but they would fight and defend their sister states, and themselves, from being attacked.
If you will note the Arkansas Convention and The Tennessee legislature both approved secession on the same day (May 6th, 1861) The only difference was that the Tennessee Ordinance required a Referendum vote for final approval, and these two states were only followed by North Carolina, who was then completely surrounded by Confederate states and cut-off from the rest of the United States, was the last of the 11 states to join the Confederacy.