Answer :
Because he was short and thought that the territories were not viable for making money because they were full of Native Americans and there was no gold or anything, only furs. But T Jefferson was able to more than double the size of the country in one purchase.
Napoleon realized that his army was stretched too thin as it was in trying to hold Europe. The loss of Haiti to a slave revolt led him to abandon his dreams of conquering the new world so he sold Louisiana to the first buyer which came along in order to finance his domestic European wars
