I'm not sure the attacks can be considered PR stunts.

Undermining Arab regimes has been tried, and has failed. AQ and associated fundamentalist groups have never been able to muster anything close to a credible threat to any significant Arab government. The main target was Saudi Arabia, and they failed miserably there. Many Saudis are perfectly happy to support AQ as long as they are fighting infidels somewhere far away, but when they propose to take over Saudi Arabia the support dies.

The only narrative that's ever really worked for them is the jihad against the foreign invader, and without a foreign invader to fight their status and credibility wane rapidly, as they did after the Soviet withdrawal from Afghanistan. Seems to me the attacks aren't just PR, they're an effort to bait the US into coming after them. Of course AQ won't win those battles, but keeping the battles going keeps them relevant, and they may think they can wear us down and win the war.