When in 2001 GWB chose between overturning the Talibanders and nation-building, letting Afghanistan be a base for terrorists who would hit the US again and again and ... again, or reducing Afghanistan to the Stone Age, he should have let the terrorists hit the US again and again and ... again or reduce Afghanistan to the Stone Age?
Maybe, 20 years in retrospect, he should have done the latter, but absent the past 20 years' experience the world-wide consequences for doing that would probably have been pretty awful.