Also AI makes mistakes. If you ever coded with AI agent you know that loop "write trash => compile => fix compilation errors => repeat" (if there are no compilation errors, there are definitely logic errors to be fixed). In real world cost of attempt is huge. You need a lot of money and you risk to draw a lot of attention if you perform long series of iterative experiments to create working virus.

In case with bomb it means that even if you have AI which gives you recipe of the bomb, but you will explode your garage and yourself with a decent chance. So you probably need to setup a good experimental pipeline (hardened lab where you can try different formulas and see that happens without being killed) if you want to go beyond publicly known explosives available in pre-AI era to anyone who read school/university chemistry books. And this also requires resources and draws attention.

People extrapolate programming experience (the area where experiments are cheap, cannot kill you and provide detailed feedback what went wrong) to real life.

I also would like to hope that people that are likely to do such things are probably:

A) don't know how to break even the most basic guardrails of models

B) already in glasswings project

To prove point B - Theranos existed.