Explanation of Hadith on Authority of Quraish

Narrated Ibn `Umar: > The Prophet (ﷺ) said, "Authority of ruling will remain with Quraish, even if only two of them remained." Sahih Bukhari Can you explain why the ruling should be from Quraish? What is the scope of the ruling? If a government is not from Quraish, then will it not be considered as an islamic government? (we had non Quraish like Ottoman)