The south's money/economy was dependent upon slavery, that is true. But every single southern state listed the right to own slaves as one of their reasons for secession.
https://www.battlefields.org/learn/primary-sources/declarati...
https://www.battlefields.org/learn/primary-sources/declarati...
Here is a transcript of Arkansas’s Ordinance of Secession: https://digitalheritage.arkansas.gov/cgi/viewcontent.cgi?fil...
Note that there is no mention of slavery.
I have read a ton of contemporary writings by the various politicians who signed Arkansas’s OoS, and with a couple of exceptions the vast majority claimed at the time to have supported secession in response to the military actions of the Union. There were relatively few slaveholders in the state at the time, and they were largely concentrated in the Delta, along the border with Mississippi.