Why did the Louisiana purchase happen?

France held its territory of Louisiana and had plans to use it in parallel to its other colony of Haiti to create a large slavery and sugarcane production business. However, this failed and Louisiana was just a barren wasteland to them. At the same time, the US was looking to expand its borders but was only looking at France's port of New Orleans. The US went to France offering over three million dollars for the city and port of New Orleans. However, France said they'd give all of Louisiana for just fifteen million dollars. The Americans couldn't resist such a deal and accepted. Thus concludes the Louisiana Purchase.