Why did the delegates to the Constitutional Convention adopt the Great Compromise?
They knew neither side would back down, and this way they'd at least get a little of what they wanted.
States with generally larger populations wanted the number of representatives to be based on a state's population. Generally smaller states wanted it to be 2 representatives per state no matter what, so they would get the same say as a much bigger state. The compromise made both and required bills to pass through both: The House of Representatives (What bigger states wanted) and the Senate (What the smaller ones wanted).