And they've still got naive people like you believing it had something to do with morals.
Let’s go through your ridiculous and highly flawed attempt at logic.
You have finally agreed that they were seeking to make the territories into ‘slave-states’. Good, that is a very small start on the long road back to reality !
But then you posit the claim that they would be ‘slave-states’ in name only. For the reason that there no good land to grow cotton and therefore no profit.
So then the state would only be a ‘slave-state’ by name and not reality.
Anti-slavery officials would be elected; slavery would be banned; and New York would (in your fantasy world) be in control.
So they must make the ‘slave-states’ real.
They must control maintain control of the state (50%+1) or they lose.
Which means that they must make the state a slave state in reality, and find a good economic use for their slaves in the state.
Now I know it is difficult for slavers to understand people with morals since they lack the same.
But the long and the short of the case is, it was the moral issue.
The issue of Emancipation/Slavery dominated the political debates; dominated the legislative issues; it dominated in the media and it dominated in the courts.
The Republicans continuously attempted to appease sore loser Breckinridge’s ‘fire eaters’ so that a war could be avoided and the issue resolved in an amicable and peaceful manner.
But Breckinridge’s ‘fire eaters’ wanted no compromise. They wanted a bloody war. They initiated a bloody war. And then they lost the bloody war that they had initiated.
Here is where you have a serious dichotomy. Slave states without any significant number of slaves are not really slave states.
They are basically free states that are allied with the congressional representation of actual slave states. What is being fought over here is the power in Washington DC, not whether or not there were actual slaves in the territories.
Again, there were still slaves in Pennsylvania up until the 1840s, and slaves in Delaware up until 1865.
Which means that they must make the state a slave state in reality, and find a good economic use for their slaves in the state.
You cannot make economics work out contrary to reality. This is socialist thinking. The reason why there were nearly half a million slaves in Mississippi was because it was economically feasible. It was only economically feasible because the land, the climate, the transportation network for product were all right. Such would not have been the case in the vast bulk of the territories, and even in that little bit of Southern Kansas that nowadays grows some cotton, there likely wasn't the transportation infrastructure in 1860 to make it feasible. We have big rig trucks nowadays.
But the long and the short of the case is, it was the moral issue.
It was presented as a "moral" issue, but in reality it was an economic issue for those having the power to determine the outcome. The "moral" issue was just the hood ornament for the larger underlying money involved in the affair. It put a public face on what was at the very base of the issue, greed and Northern control of economic activity in the entire nation.
This is why they were willing to pass the Corwin amendment. They didn't actually care about slavery, they cared about keeping control of all the economic activity in the nation.