The next to last image is of Palladio's Teatro Olimpico, which was completed in 1585. While this was certainly after Christianity and the iconostasis' implementation, but his architecture was largly based on Ancient Greco-Roman architecture.
Is it just a coincidence or do you think they Christianized this?
I think you have hit on your explanation.
The iconstasis as we know it doesn't come until the emphasis on iconography after the Triumph of Orthodoxy. When they wanted to built large walls with three doors, that example of the theater was there as a blue print of how to do that. But to be a direct development, we would have to have early Churches displaying such an affinity, which we don't: they are based on the basilica (which is how Romanian gets its name for Church: "biserica."
Some however, do see a direct descent via the templon:
Yes, the templon definitely does predate the iconostasis, I think that is actually what the Hagia Sophia once had.
In the wikipedia article you quoted it says:
The templon most likely has an independent origin from that of Latin chancel barriers. Classical stage architecture is one possible source. At certain times during Byzantine history, theater heavily influenced painting and sculpture. Architects then, influenced by stage backdrops dating back to Sophocles, consciously imitated the classical proscenium (the backdrop of a classical Greek stage), copying the multiple columns punctuated by a large door in the middle and two smaller doors to each side. The statues on top of the backdrop would thus be analogous to the icons of the saints looking down. The similarities, however, are probably only visual. Although classical drama was performed in Constantinople, the capital of the Byzantine Empire, during the 5th and 6th century when the first templa appear, when Christian liturgy was first being developed, the plays and their architecture had lost their importance and could not have influenced Christian ritual. (Emphasis mine)
However the article then goes on to discuss how the more probable source is the Torah screen in Jewish synagogues
I think it is interesting though, I would tend to be on the side of both/and. I think it comes from both the Classical Roman/Greek background, and the Jewish Background. It also of course, has it's own unique aspects which weren't entirely in either tradition.
Just as an interesting side-note, it appears that the templon started appearing in the 5th Century. This was during the time of people like, St. John Chrysostom, St. Cyril of Alexandria, St. Jerome, St. John Cassian, St. Leo I, St. Augustine, St. Patrick, St. Boniface.
It was also when Nestorius & Pelagius preached their heresies. As well as when Attila and the Huns came into Europe, and eventually when the Western Roman Empire collapsed under barbarian attacks.