John 7:20

Many of Jesus’ hearers did not realize the depth of the animosity of Israel’s leaders toward Him. They naively thought He was crazy to think that someone was trying to kill Him. The Jews of Jesus’ day commonly thought of mental illness, in this case paranoia, as being demon-induced. This explains their reference to Jesus having a demon (cf. John 10:20). These people were not charging Jesus with getting His power from Satan, as others had (Matthew 9:34; Matthew 10:25; Matthew 12:24; Mark 3:22; Luke 11:15; cf. Matthew 11:18). There are several cases of demon possession in the Synoptics, but there are none in John.