For the reasons stated above, to be sure. I would add that the method of attack, using hijacked planes full of involuntary victims as a suicide bomb, was designed to be high profile and to spread terror.
Hitting the World Trade Center was intentional, in that it panicked our financial markets and was instrumental in causing a recession. In other words, the fear they caused with these attacks hurt our economy, exactly as planned.
Al-Qaeda was not sponsored by any nation state, they were acting as an independent group with unconventional methods of fighting.
The attacks were designed to topple the WTC buildings (bin Laden is a civil engineer by training), and timed separately, so that one strike would look like a horrible accident, and the second strike would instantly spread the terrible knowledge that we were under attack.