Why was missouri territorial governor against the idea of slowly getting rid of slavery in missouri?

There were many reasons. For starters, the entire economy was based around slaves working on plantations of things like tobacco or for making gin. Without them the state would break down because they wouldn't have the free workforce that they had when they had slaves. Also, it would also help the northern states and abolitionists since there would be more non slave than slave states.

The mountains on the east would be taller