My experience and what is written in the text books align on this subject. Children with accommodative esotropia often present around the age of 3 years old. The reason for this is at this age children start to look at and focus more on near things. If they go to nursery (kindergarten) they will do lots of near tasks; painting, messy play, looking a pictures in books, learning to write.
Even if they are looked after by a parent or childminder they will be doing more near tasks than in the previous 3 years. Of course, in order to see clearly at near young children will accommodate and if they have unknown hyperopia they will have enough accommodative amplitude to focus through large amounts of it.
The extra accommodative effort will also drive convergence (because of the near vision triad) and this is what causes the esotropia. This could be further complicated by a high AC/A ratio. It is important to find and correct all the hyperopia to prevent a fully accommodative esotropia converting to a partially accommodative esotropia. These are much more difficult to treat.