A 58-year-old man with hypertension and type 2 diabetes mellitus is posted for elective laparoscopic cholecystectomy. After induction with propofol (2 mg/kg IV) and succinylcholine (1.5 mg/kg IV), intubation is completed. Within 2 minutes of starting positive pressure ventilation, SpO₂ drops from 98% to 88%, and blood pressure falls from 140/90 mmHg to 85/50 mmHg. Breath sounds are equal bilaterally. End-tidal CO₂ is 32 mmHg. What is the most likely cause of hypoxia in this scenario?