Jamieson, Fausset and Brown on John 12:37-41

37-41. It is the manner of this Evangelist alone to record his own reflections on the scenes he describes; but here, having arrived at what was virtually the close of our Lord's public ministry, he casts an affecting glance over the fruitlessness of His whole ministry on the bulk of the now doomed people.

though he had done so many miracles--The word used suggests their nature as well as number.