What was one main reason why slave trade greatly expanded beginning around the 1500s?

Slave trade in the 1500’s expanded coincidentally at the time where Europeans where discovering or conquering new lands in the Americas. Well, the Europeans had already decimated the native populations in the Americas and so have so much land yet so few people to farm or develop it. The solution is to import slaves from Africa, so they tapped the already-established slave trade there. The trade proved very lucrative to slave traders, who set out more expeditions to capture slaves in Africa to sustain the increasing demand from the Europeans.

it further strained relations between the north and the south and convinced

congress also has implied powers, which derive from the necessary and proper clause of the constitution and permit congress "to make all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this constitution in the government of the united states.