In this article, an English historian claims that Napoleon fled Waterloo so quickly in part because some of his enemies (specifically Prussia) had threatened to have him executed. I know that there were some assassination attempts on Napoleon I, but was this actually the case - that European powers wanted to have him executed in captivity?
While Andrew Roberts is a bit of a Bonapartist, he is correct. Prussia wanted Napoleon dead. There was a bit of fear involved, fearing that he would end up rising again but there was more interest in revenge. While Austria had been soundly defeated several times and Russia was one of Napoleons longest term enemies, but Prussia had the worst defeats and greatest humiliation (Jena is a textbook Napoleonic battle due to Prussian inflexibility).
Wellington had no interest in more blood, but knew of an island almost in e middle of nowhere that he stopped at during his time in the wars against India. It was out of the way and could easily ensure that Napoleon would never leave.