People in some Middle Eastern countries use the name of god so frequently that these words are becoming familiar even in the west:. Inshallah, wallah, ilhamdulillah, mashallah, yallah (i think) and probably a few more. For less religious people these are just phrases they use without thinking twice, but the more religious are quite conscious of their literal meaning when they say them.
So if the candidate is from the Middle East, it may just be a bad translation, or it means that the candidate is quite religious.
This is just anecdotical, but I personally have told several quite religious people from the Middle East that I have no religion and I have not gotten any (visibly) negative reaction yet. So I would not automatically assume that a religious candidate from these countries will have problems tolerating other views. These countries have different degrees of piousness too, and anyway if he/she moves abroad, they are probably aware that they have to adapt to their new environment.
Obviously the letter you received (if it was indeed from the middle east) was not particularly well-adapted to western culture, but then one might first need to become familiar with western culture before one can adapt to it.
P.S. as a native speaker of German, I quite often use Gott sei Dank (thank god) in everyday life. I would not use it in any formal letter because it is a somewhat informal expression. But it probably would not occur to me that using such a phrase might be culturally inapptopriateinappropriate.