This is pretty naive. Distributing computing has existed since forever. It would run significantly more slowly, but there is nothing theoretically stopping the "LLM broke out of containment and moved itself elsewhere" boogie man from becoming a reality. The available exploitable compute from unsecured IoT devices is pretty substantial as things like the Mirai botnet have shown. While this isn't the most easily distributed problem, there is no fundamental issue here. [Edit: it also wouldn't need to "exfiltrate itself" to cause persistent harm. Could easily just install malware on infected hosts]

AI isn't "dumb" in a practical real world sense. LLMs have shown themselves capable of exploitation on the open Internet and of finding zero day vulnerabilities. Do you have any idea how much of our critical infrastructure can be reachable by some sort of network? LLMs have shown themselves capable of manipulating people via speech. None of this requires some sort of "super intelligence" and it doesn't even require some sort of provable intelligence: it's all quite possible as things currently stand right now.

These may not be "the entire future is over" level issues, but there is significant risk here and it shouldn't be ignored just because we think AI companies are horrible. Is an LLM going to make us all batteries or paper clips? No, but it could cause significant physical and/or economic harm temporarily.