Wow,
Have you guys actually talked to any of these converts, or are you just spouting off? I personally know several converts to EO - from Baptist, Reformed, and Lutheran backgrounds.
On a social level, the answer is fairly obvious. EO has had virtually no presence in the USA until recent decades. They've just now gotten together some seminaries, a publishing house, and some network, so their influence is just now being felt.
But we're probably talking mostly about personal justifications. Here are some reasons I've heard:
1. Unity - converts to EO generally believe in the ideal of a single church, but don't buy the arguments for papal supremacy
2. Historical Liturgy - Many EO churches still have rites demonstrably similar to ancient (3-5 cent.) rites, thus reinforcing the idea of doctrinal continuity
3. Aesthetic Liturgy - Many converts to EO vigorously deny the "spiritualism" of Calvinism, asserting on incarnational grounds that the material is the proper channel for mediating the spiritual; they see Protestant (Calvinist) worship as bypassing the material and as being overly logo-centric
4. Anthropology/Soteriology - Many converts to EO see the West as being preoccupied with theories of original sin, merit, and consequently justification, and believe that their system of deification manages to avoid this; you might say that the East rejects both sides of the Augustine/Pelagian controversy
Lutherans seem to be getting hit particularly hard. I was talking to a Lutheran to EO convert and he said that at least 12 of his colleagues from seminary (LCMS) went East. Part of this may have been because of a surge of scholarship connecting Luther to certain Greek patristic theologians.
I think postmodernism is way off the mark as an explanation. Many EO's view postmodernity as being a Western problem. Catholics have a history of blaming Protestants for modernism, and the EO's have co-opted that line of argumentation to blame the whole West for the whole mess. Even some Westerners agree. The late Colin Gunton articulated this; see his
The One, The Three, and the Many: God, Creation, and the Culture of Modernity. A recent work by an evangelical critiquing this narrative is Bradley Green,
Colin Gunton and the Failure of Augustine. I have a
published book review in Augustinian Studies.