He just wanted to show that he is going for some diplomatic job. The same thing he did it for his UK trip. He and Gujarat administration had aanounced that Modi is going to UK for business purposes under invitation from them. The organisers made it clear that they never invited Modi and he is coming on his own for some musical concert.
I dont understand why he do this. He can go any place on his own. Nobody have any objection. Its upto him. But dont say its an official trip. I think most polititians do this. They just go in name of official trip enjoy it and come back at the expense of the state. Modi too.