When the British uses force on the colonies they rebel against British by throwing several act which includes the Boston tea party and also the formation of salutary neglect.
It was possible because it helped him navigate in territories that were completely unknown to him. Thanks to it, he could determine where his ship was based on the position of the sun and the time of the day and he used this to navigate all the way to India.
The North realized that if it did not act swiftly, the Southern states might take the precedent of the Scott case as a justification for expanding slavery into new territories and free states alike. The South recognized the threat of the Republican party and knew that the party had gained a considerable amount of support as a result of the Northern paranoia in the aftermath of the decision.
