It's like a movie scene where top scientists from AI labs are working to solve the alignment problem and Jeff Bridges knocks on the door and says "hey guys, have you thought about unplugging the damn thing"?
You are assuming a centralized super intelligence is better than multiple separate intelligences. Maybe controlling hardware (bodies) is very hard to do in a centralized fashion. Maybe the delay in transmitting commands is too high to allow for a centralized processing unit to handle it and that's why animals have evolved as many separate individuals.
Humans and other animals have evolved during millions of years of evolution. We might be very efficient collectively. A single centralized intelligence might not be very efficient or even possible. We might just kick its ass and take leaps around it. We don't know. Claiming every new step in our discovery might bring the end of humanity it's like when they built the Eiffel tower and all the farmers around were scared it would collapse and kill everyone.
THE WOLF, THE WOLF, THE AI WOLF! https://en.wikipedia.org/wiki/The_Boy_Who_Cried_Wolf
Since the AI works much slower than you it can not prevent you from unplugging it. Even maintaining such a compute cluster requires work from humans both on the hardware and software side. People could just stop working on it and it would eventually fall over.
>It's so trivial that you cannot shutdown a system that it boggles me
Virality doesn't require sophisticated AI so it can get away with simpler code that can run on any system.