A 3-day-old male neonate born to a 28-year-old primigravida presents with bilious vomiting and abdominal distension. On examination, the abdomen is mildly tender without peritonitis. Plain abdominal X-ray shows a 'double bubble' sign. Upper GI contrast study reveals the duodenum crossing the midline from right to left, with the jejunum and ileum positioned on the right side of the abdomen. What is the embryological basis of this anomaly?