Malposition of the NG tube.  Given the bronchial anatomy, if an NG tube enters the trachea, it is most likely to end up in the right lower lobe because its bronchus is most vertical and in line with the trachea.

The tip of the tube appears to be below the diaphragm, but this is just because the tube as entered the posterior segment and is projected below the level of the anterior diaphragm.

Certainly an enthusiastic attempt at NG insertion.