>The bottleneck is usually the actual physical execution in the real world, not theoretical knowledge.
And the interest or willpower too. People fall into a kind of reductive Good vs Evil mode of thinking, with "terrorists" being of course a kind of shadowy mass of pure evil lurking in the darkness. But actual real life terrorists are people too and I'd wager few of them are actually interested in trying to end humanity.
The only terrorists who wanted to end the world were Aum Shinrikyo as far as I remember. Everyone else is fighting for a cause that benefits their people - some good like kicking out colonial oppression, some evil like fascism or Islamism, some of them in between like various ethnic conflicts.
Even the religious extremists don't really want to take over the world and destroy everyone who doesn't convert. That's just a way to gain support from a conservative nation. A lot of them are motivated by revenge for wars that destroyed their country and want to make sure it never happens again.
Their methods are wrong no doubt, and not very effective, but the reasons they do it are good. And a person like that will never release a deadly bio weapon. We should worry more about incel mass shooter types who believe everyone is evil.
Exactly. I am more worried about a Beavis-and-Butthead lone wolf incel type making something that kills a thousand people and then scale that up across 4chan or whatever. Not human extinction but still very bad.