What are the reasons and prerequisites for the emergence of the Old Russian state?

We are talking about the IX-X century. The reasons can be divided into the following groups:

Defense against a military threat. Such were the Khazars (until 969) and Pechenegs (from 972 to 1036), the Hungarians – at the end of IX, during the resettlement from the Volga to their modern territory.
Economic. Within the framework of a single state, it was more convenient to control the trade route “from the Varangians to the Greeks” along the Dnieper and Volkhov. Division of labor, the squad stood out, it helped the first princes in management.
Political. Strengthening the sole power of the princes. For example, in 862 the Varangians were called up, and 20 years later, Prince Oleg made a campaign against Kiev, killed the local rulers – Askold and Dir and subdued the city.