Salam Alukom
In addition to what brothers and sisters mentioned, there are other two reasons that Allah made Adam and Eve enter the pradise and got out of it again; which are, fristly, giving them a practical experience of the Devil's misleading. For sure they got it theoretically, but the practical one is more remarkable.

Secondly, to give them another practical lesson of how dangerous it to disobey Allah, how to ask God's forgiveness.