Why? His drama comes from life experience in high pressure politics.
Fredrick Forsyth was a pilot for the British Air Force, a spy in cold war Germany, and a reporter during the famine in Biafra in the 1960s.
As a writer, those experiences are as good as gold.
His most famous work, Day of the Jackal, is based on a true life incident about the attempted assassination of the French premier. It is told in the viewpoint of the assassin. Forsyth is so good, by the end of the book you are rooting for the assassination to take place.
His second book is titled, The Odessa File. After World War 2, many Nazis took up prominent positions in German society. The Odessa File was a list of these. Many Germans, along with officials from Great Britain, the US, and France, were willing to look the other way. Ironically it was the Communist East German government that offered valuable cooperation in bringing these criminals to justice. For justice sake the world is lucky that many dedicated Jewish Nazi hunters would not forgive or forget.
Forsyth wrote great historical fiction from an eye witness point of view.