What EXACTLY do they mean when they say that AI could cause an extinction event?

Seriously! I understand that current frontier models currently surpass the intelligence of any single human. However, as something of an AI power user, I have a hard time imagining how a super powerful model could ‘end the world’ by breaking out of containment. Maybe I just lack creativity, but I really feel like it’s a sensationalist ploy to get attention. Does anyone have insight into this?