Scale! Do this to two people, no problem you can get a team of folks to dig through their social media, come up with a plan, execute. Might take a day to get a good crisis cooked up.

An AI might be able to run this attack against the entire planet, all at once.

Try to think like a not-human, and give yourself the capacity of near-infinite scale. What could you do? Human systems are hilariously easy to disrupt and you don't need nukes to make that happen.