Why was Napoleon sent to Elba after his first abdication?

Following his first abdication on April 6, 1814, Napoleon was sent to Elba as part of the terms established by the Treaty of Fontainebleau.

Facing overwhelming military pressure from the allied forces of Austria, Russia, Prussia, and Great Britain, and witnessing the collapse of support in Paris, Napoleon concluded that further resistance was futile. Under the treaty, the allies granted him sovereignty over the island, allowed him to retain his title of emperor, provided an annual income, and permitted him a small guard of volunteers. This arrangement effectively removed him from the French throne while granting him a status that acknowledged his former position, rather than treating him as a common prisoner at that time.12