What terrorist attack had been carried out by al-Qaeda in 1993?
I think you mean the World Trade Center Bombing in 1993. This was not an Al Qaeda operation.
Ramzi Yousef from Kuwait was the primary instigator. He got advice and finances from his uncle Khalid Shaikh Mohammed Ali Fadden who went on to be an important part of the September 11, 2001, WTC attack.
Yousef's motivation seemed to be a reaction against US support of Israel actions against the Palestinians.
Al Qaeda was created in 1988 and had a larger strategic goal getting the US to react to terrorist attacks by getting into ground operations in the Middle East or Afghanistan. This, it was thought, would eventually lead to a collapse of US hegemony like the the collapse of Soviet Russia. This followed the pattern of defeat of the the Soviets in Afghanistan created the collapse of the Soviet State.
Historically the Soviet withdrawal from Afghanistan is only part of the story of the Soviet collapse.
Yousef's planning did not seem to be part of a larger Strategy other than to make an attack on US territory.