They did not. Slavery had been a fact for millennia before suger plantations were introduced.
Europeans had started huge sugar and tobacco plantations in the Americas. They needed large numbers of workers for these plantations, and slavery was one way to get them
tobacco and sugar plantations
because Cuba wanted U.S. to help them only way to get their attention was by burning the sugar plantations of American investors
"Worked" is a generous way to put it. Black were enslavedon plantations.
Africans settled on white-owned plantations due to the forced labor system of slavery, where they were owned by white landowners. Illegal unions were formed as a way for enslaved individuals to seek companionship and resist the dehumanizing conditions of slavery.
Europeans wanted slaves in the Americas to provide cheap labor for their plantations and mining operations. Slavery allowed them to profit from growing crops like sugar, tobacco, and cotton without having to pay wages to the laborers. Slavery was also seen as a way to exert control and dominance over indigenous populations.
Slavery existed because it was cheaper to run the plantation because they don't have to pay the slaves. The plantation owner didn't have to do all of the backbreaking work and all of the crops will come in quicker because he has lots of people do the work.
Plantations could not run without huge amounts of labor. Which is where slavery comes in. Many plantation owners needed cheap labor, so slaves were the easiest and quickest way to get that.
The Northwest Ordinance of 1787 prohibited slavery in the Northwest Territory (modern-day Midwest states) north of the Ohio River, setting a precedent for restricting slavery in new states. This limited the expansion of slavery into these territories and helped pave the way for future anti-slavery efforts in the United States.
pave the way?
Most Southerners viewed slavery as necessary for their economy and way of life. They believed it was a vital institution that provided labor for their plantations and farms. Many saw slavery as a fundamental part of their culture and were resistant to any efforts to abolish it.
Slavery was a divisive issue during the drafting of the U.S. Constitution, with compromises such as the Three-Fifths Compromise and the Fugitive Slave Clause included to appease slaveholding states. The Constitution did not abolish slavery but did pave the way for its eventual abolition through amendments like the Thirteenth Amendment.