But I think the key failure here, in your thinking, is that you can't conceive of something, and that therefore something can't happen, and you're doing that in the context of things that are smarter than you. You being able to conceive of it is simply not required for it to happen.
Also, Colossus: The Forbin Project was a great movie from 1970 on this subject. Spoilers: an AI takes control of the nuclear arsenal and then threatens humans with extinction if they do not serve it. The humans do serve it, of course, because the humans in charge don't want to die, and are entirely fine with enslaving the rest of us.
The book superintelligence by Nick Bostrom gets into the fine details of all the different ways an AI would escape, why it would escape, and why it wouldn't take a chance with a species that murders its own kind for fun and profit.