Wrote this elsewhere, but I think its worth thinking about a scenario like the book "daemon", rather than a "super-intelligence explosion" type scenario (which may be more like curing the cold or fusion than building a faster car).
All it really takes to do some kind of crazy world-dominating thing is some simple mechanisms and base intelligence, which the machines already possess. Using basic tactics like coercion, spoofing, threats, financial leverage, an unsophisticated attacker could cause major damage.
For example, that Meta exec who had their email deleted. Imagine instead one email had a malicious prompt which the bot obeyed. That prompt simply emailed everyone in her contacts list telling them to do something urgently (and possibly prompting other bots who are reading those emails). You could pretty quickly do something like cause a market crash, a nationwide panic, or maybe even an international conflict with no "super intelligence" needed, just human negligence, short-sightedness, and laziness.
Examples would be things like saying there is a threat incoming, a CIA source said so. Another would be that everyone will be fired, Meta is going bankrupt, etc. Its very easy to craft a prompt like that and fire it off to all the execs you can find (or just fire off random emails with plausible sounding emails). Then you just need to hit one and might set off a cascade.