Read the texas secession ordinance. It makes it abundantly clear Texas succession was over slavery. Take it down.
Read Lincoln’s Inaugural address or the Corwin Amendment. Those both make it abundantly clear slavery was not threatened.
I'm going to present you with something that you may find very confusing.
Slavery was legal in the United States in 1861. It was literally impossible to make it illegal, and Lincoln tried to offer the South even stronger protection for it.
Therefore the real reason for leaving had nothing to do with slavery.
secession