Intelligent terrorists?

There are lot of factors which point out that terrorists are intelligent beings.They attacked during the tourist season when the hotels are full.They hijacked indian vessel and entered our country.Also some of the terrorists tied red ceremonial threads on their wrists to appear like Indian fishermen.(show how aware they were of our weaknesses).They were trained to locate their targets on a high-resolution satellite map.How could people so intelligent be brainwashed to actually kill others?This is sad that people with some semblance of sense are terrorists and killers.But its strange question comes to my mind,what did they want?what did they prove?.Seems like mentally ill people.