It was popular in Baghdad until the 5th century and Basra until the 6th century.
It also spread through much of Khorasan, Faris, Yemen, and Al-Shaam.
4) Ahmad's madhhab only spread through Iraq and Al-Shaam initially.
The other Awza'i stronghold in Al-Andalus didn't last too long either. It only lasted until the third century.
8) Al-Tabari's madhhab also did not last too long and dwindled in the fifth century.
10) Al-Thawri's madhhab lasted at least until the 8th century.
Naturally, the endorsement of an empire of a madhhab will cause it to spread.
He states, "Those that followed other madhhabs were treated as enemies and were condemned. He who wasn't a follower of one of them...
The scholars of the lands proclaimed that it was obligatory to follow one of the four (madhahib), and prohibited following the others."