Iblis swore by God when he didn't even believe in God. It didn't click in Adam's (a) mind someone would use God like that because of Adam's (a) own truthful nature. At the same time, Adam (a), if he didn't eat of the tree (envy their station) - there would be no deviance and evil would be subdued. But when the human leader envied the chosen status of the exalted ones (translated as "gods" in the Bible) and doubted the veils himself - he became ashamed and as well as the consequences of his sin, people witnessing in the unseen realm, began to take sides of Iblis as well (before being born) so God decided to make a world of sufferings, death, and trials whence some of us are enemies to each other and thereby there would be more chance of reforming us and keeping us from following the path Iblis.
While Adam (a) doubted the veils, he believed in God, but thought Iblis worshiped and believed in a different God that wanted Adam (a) to compete and take the highest position. He thought he can attain their rank through competition and when he envied their station, he fell from grace.
Ultimately, it was a confusing matter for him, but if he held on to the love of Ahlulbayt (a), he would be firmly on the right path and this world would not be needed to come.
According to tafsir Hassan Al-Askari (a), when he turned to God through them though, God accepted his repentance and restored him to his chosen status. This means, because Adam (a) in a way forgot God and was not insolent arrogantly and was not stubborn in his sin, his chosen status was not all diminished by Iblis' lies.
Adam (a) was able to realize he left the realm of light and started to cover himself with "leaves" of the garden, but Iblis, when he was kicked out the realm, took on the living form of ignorance and believes he is right.
So while Adam (a) believes in truthfulness, lying and deception is fair game for Iblis.
While Adam (a) wants to have honor and dignity in sexual activity - Iblis believes there is nothing wrong with all sexual acts and nothing to be ashamed of in all these acts.
Iblis understanding of moral light is deviated, but has become so ignorant he believes he is correct.
He witnesses the power of Prophets (a) and chosen Guides (a) but denies the source of their power and accuses it to be just sorcery inherited from one person to another.
The devils witness the sky and power of Angels therein and chosen lights (the visited family), but still disbelieve in all that, and are war with the order of the universe. The devils believe they are guided and are our to be our guardian Angels, but they act to envy of God's chosen, but tell and deceive themselves they are guided and good.