I have often wondered who the seven congregations in the book of revelations were and why they were mentioned. It seems that they are all a group of towns situated in the east of Turkey near the coast with the Isle of Patmos nearby.
Perhaps this group was a circuit that an overseer looked after. Their central committee in Jerusalem assigned an overseer to an area of congregations, and he would visit each one in turn, maybe during the course of the year, to see how they were doing and to give advice. If John was that overseer he was imprisoned on Patmos he would not be able to look after them. Patmos is geographically next to these seven congregations. If so then he was worried about them. Jesus Christ responded to his concerns with expert advice and encouragement for them.
Maybe with the changes occurring in the world it was the last of the circuit overseer’s advice they would get from an original disciple. John was in his 70’s and Jerusalem was close to or had been attacked and destroyed by the Romans in 70CE.