Note that the Orientation Slice is cut precisely to the (100) before the crystal is rotated and cut at either +.25 degrees and toward the flat, or â.25 degrees and away from the flat (as described in Figure 3).
The era was called the Dark Ages also because we don't have a lot of written sources from that time period, especially from the early part of the dark ages (500 to 800 CE).
Thus, the answer to the question as asked is, no, Christianity did not cause any dark ages, and the Middle Ages (a more accurate description of the time from Constantine to the Renaissance/Reformation) was a time of complex factors.