Abu Yusuf's tenure as chief judge under the Abbasid caliphate gave the Hanafi school an early and lasting advantage that had little to do with theological argument: state patronage. Judicial appointments across the empire favored Hanafi trained jurists, and the school became the default legal framework of the courts even in regions where other schools were more common among the general population. That pattern repeated under later Muslim states.
The Seljuk Turks, and the Turkic and Central Asian dynasties that followed them, carried Hanafi law eastward and into the steppe; the Mughal empire made it the law of its Indian courts, shaping legal practice across the subcontinent regardless of the much larger Shafii and other populations it governed in some regions; and the Ottoman empire adopted it as state law across territory stretching from the Balkans to the Hijaz.
Ottoman use of Hanafi law reached its most systematic form in the Mecelle, drafted between 1869 and 1876, which set out Hanafi rules of civil transaction and obligation in the numbered articles of a modern legal code, the first such codification anywhere in the Islamic legal tradition and a model that influenced civil codes across the post-Ottoman Middle East long after the empire itself ended.
Today the Hanafi school is followed, by most estimates, by a larger number of Muslims than any of the other three surviving Sunni schools, Maliki, Shafii and Hanbali. Its geographic core runs from Turkey and the Balkans through the Levant, the Caucasus and Central Asia into South Asia, a footprint that traces the old Ottoman, Mughal and Central Asian Turkic states almost exactly, evidence of how thoroughly a legal school's reach can be shaped by which empires adopted it rather than by argument alone.