About the claim at the end:
Historians debate about whether terrorist groups are destined to fail or not. Some say that authentic terrorist organizations achieve partial goals only. Many regard John Brown (approx. 150 years ago) as the most successful terrorist till this day – But you might read the essays: "How Successful Is Terrorism?" (James M. Lutz and Brenda J. Lutz) and "Why Terrorism Does Not Work" (M. Abrahms) and you will find out what this message is exactly about: Deterring potential future terrorism by education.
Due to the large amount of data used, there are likely to be mistakes (exact chronology, location, casualties etc.). This video should serve as an approximation. (Especcially in the messy parts.)
Typical issue would be: GTD had sometimes the "at least" casualties or it splitted one terrorist incident into many (Istanbul Bombings of 2003, Casablanca bombings of 2003). This is why some incidences are not accurately represented on the map. It's a tiny fraction though. Also, I like to point out that I used different definitions of terrorism regarding the area and time of attacks.