The church is deluged with denominational attitudes. Sectarian teaching has found its way into many pulpits and into the classrooms in many of our schools and universities. John gives us an apostolic view of the causes of such apostasy. They were not 'of' the disciples, i.e., they did not possess the same spirit of obedience characteristic of the disciples, for if 'they had they would have continued with' the disciples. The Bible presents varied reasons for the infection and spread of the disease of apostasy.
Deception is one reason for division.
And no marvel, for Satan himself is transformed into an angel of light. Obedience was minimized. Many followed Moser because he showed an irenic spirit, however contrived that spirit might have been. There are convincing personalities in this generation who are using the same strategy to draw away many disciples into accepting their favorite theories of grace only, and change of the unchangeable, and mutating the immutable. Diotrephes wanted to be the petted and pampered.