Slavery was very prominent in the south, and in order to please southern states, the founding fathers allowed slave trade to continue until 1808 (which wouldn't be in effect until 20 years after the constitution was ratified). Some of the framers themselves owned slaves, however they understood this was not a good thing for the country. They had to appease the south, because if they just banned slavery then the south would have not ratified the constitution. The founding fathers began to see tension between abolitionists and proslavery supporters, thus fearing a division between the two. The framers attempted to create early unity between the two, however it crumbled leading to the civil war.
Ultimately, the framers legitimately feared both division between the north and south, as well as our nation falling under a monarchy. With that being said, their actions were justified in trying to handle these fears, however, lacked many components and were very incomplete which is why issues still remained within the