Why did Troyans and Hittites conclude a treaty?

According to the treaty concluded in 1280 B. C. E. between the king of Wilusa/Ilios/Troy Alaksandu and the king of Hittites Muwattalli II, what Alaksandu had to implement was different from what the city states in West Anatolia and North Syria had been obliged to implement. With this agreement, Wilusa became a vassal Hittite city and a part of the Hittite Empire. The fact that Wilusa joined the Empire meant essentially handing down some of its rights, especially its authority over the external affairs, in the state law, to the Empire. The status of Wilusa as a part of the Empire was defined by being included in the union of the "Arzawa countries. In this way, a strong relationship of loyalty to the empire. the king, the neighbour "Arzawa countries," and especially to the Mira king, and collaboration with these parties were made possible. This loyalty and collaboration did not limit itself to contributing to the protection of the empire within and outside the state by providing military legions and war vehicles; in addition, it had to prove itself by showing independent and responsible behavior when the internal security of the empire and other vassal states were threatened.

However, at the same time, inclusion of Wilusa in the Hittite Empire provided Wilusa with protection from external threats and stability inside. A few years after the conclusion of this treaty, a historical landmark, Kadesh war between Hittite king Muwattali II and Ramses II was fought; it ended in Hittite's favor. In Egyptian scriptures, it is stated that Dardany (the main city of Troy, according to mythology, in the Troas region) joined this war supporting Hittites with twenty five war vehicles.