@czottmann it definitely achieved its aims. Before that morning, Aznar’s party was virtually guaranteed a reelection with a comfortable majority under Mariano Rajoy as leader. This attack managed to change enough of the country’s mind on who to vote for that he failed to gain a majority and was unable to form a government. And Spanish withdrawal from Iraq was the direct consequence of that.
The actions of Aznar’s government helped, yes, but this attack was well timed to have a political outcome.