Was the decision driven by a reading of the Constitution, or a knowledge that a ruling in favor of secession would rip the country to shreds anew?
I would contend that the USSC had to rule the way they did.
You may contend to your heart's content. That is your opinion and you are welcome to it. However, some evidence to support your claim would be nice and the fact that you believe the decision is not based on the Constitution does not make the Supreme Court decision invalid. A majority of the justices disagree with you and their opinion is the only ones that matter.