The wisdom of it concerns the charging of duties; Adam was sent charged with such a duty that the unfolding of all mankind's spiritual progress and the revealing of all mankind's potentialities and man's essential nature being a comprehensive mirror to all the Divine Names are the results of it.
If Adam had remained in Paradise his rank would have been fixed like that of the angels; man's potentialities would not have unfolded. In any case the angels whose ranks are unchanging are numerous and there is no need for man to perform that sort of worship. Indeed since Divine wisdom required a realm of accountability appropriate to the potentialities of man who would traverse infinite degrees he was expelled from Paradise for his well-known sin sin being the requirement of man's nature and contrary to that of the angels. That is to say just as Adam being expelled from Paradise was pure wisdom and pure mercy so is it just and right that the unbelievers should be sent to Hell.
The unbeliever only committed one sin in a short life but within the sin was infinite wrongdoing. For unbelief is an insult to the whole universe; it negates the value of all beings it denies the testimony to Divine Unity of all creatures and is contempt towards the Divine Names the manifestations of which are to be seen in the mirrors of beings. Therefore in order to avenge the rights of beings on the unbeliever the beings' monarch the All-Compelling One of Glory casts the unbelievers into Hell and this is pure right and justice. For an infinite crime demands infinite punishment.