Why is it extremely dangerous to eat the "destroying angel" mushroom?

The destroying angel mushroom has a toxin called amatoxin. When you consume this mushroom, symptoms don't appear until 5-24 hours later, when the toxin is maybe already absorbed and organ damage is irreversible. Symptoms include vomiting, cramps, delirium, convulsions, diarrhea, and death. Half a mushroom cap can kill you if you're not treated very soon.