The Founding Fathers had different characters. They were regular people and has personality flaws like everyone else.
George Washington was known for his temper. Thomas Jefferson was known to be shy. He once loved Rebecca Burwell but couldn't speak to her. The Founding Fathers were vital in shaping the United States as they made laws that will benefit the people.
When the humanity of enslaved Americans was debated, they would have felt bad and would expect an outcome that'll lead to their freedom.
The aim of the Founding Fathers was to have a government that won't give too much power to one person. This led to the separation of powers that were in the Constitution.