In general, the Ephesian people seemed to be fascinated with magic and the occult (Acts 19.19ff), which is why Paul emphasizes Christs power, authority, and triumph throughout Ephesians. In addition, this is probably a letter that was more circular, intended for many churches in the region. There are not many personal references and Paul gives lots of doctrine and application that applies across the board, likely making this his most universal letter.
The city of Ephesus was a highly cultural city, situated on the Sea and containing great wealth and many amenities. Ephesus was home to large commercial enterprises, civic structures, and the great Temple of Artemis one of the 7 wonders of the Ancient World. Thus, it was a very cosmopolitan city, harboring people from many walks of life and belief. The Temple of Artemis was tied into cult prostitution as well as status and commerce, making the idolatries of their city comfort, sex, money, and status greatly mirror those of our own. In the midst of their great idolatry, Pauls first instinct is not new and better behavior but a new and better God. He points to a Jesus more majestic and beautiful than their idolatries, The One who has power, authority, and love beyond anything they had known.