Turkish only started this service a couple of weeks earlier, so it is quite possible the crew were unfamiliar with the airport. There is an RNAV approach to this runway (again similar to the incident in Kathmandu). It is just as likely they flew the RNAV straight in from the east thinking to save time, as it is possible they were running late. One scenario is that it was still quite light when they started the approach but visibility deteriorated as they got lower. Maybe thunderstorm activity to the west was a factor in not flying the ILS or not wanting to give up on the approach. Either way with hindsight it does not seem to have been a great decision making process.