Because the battle was arranged to be fought at Kurukṣetra, which is mentioned elsewhere in the Vedas as a place of worship – even for the denizens of heaven – Srila Prabhupada BG:1.1 Purport
Ksetra means generally called as holy place. There is no difference between the Lord Krishna and his holy places.
Why is the word dharma-kṣetre used in the first verse by Dhṛtarāṣṭra?
- Dhṛtarāṣṭra knew that for the very long time people generally used this place to do Dharmic activities.
- Since it is a holy place where always allows us to increase the dharmic activities.
- This was used by the devas and devatas to perform their sacrificies.