Why are people still talking about or believing alternative theories about the JFK assassination?

[BryanDouglas81]

9. JFK: The French Connection

Why do you think that the FBI deported a known French assassin one day after the event? Jean Souetre was involved in at least one other conspiracy to eliminate a Western leader. This is a quote about Souetre from a summary of the book that I mentioned in the title of this post.

He was involved in anti-de Gaulle terrorist activities in Europe and even tried to recruit the CIA in his efforts to oust the French President. During his career, he used at least 11 identities, including those of two real people. Why was a known French assassin in Dallas on the exact day that the president of the United States was killed, and what role, if any, did he play in the monstrous deed? This book delves into major areas of study: (1) the investigation of Jean Souetre and the two other men whose identities he used; (2) the investigation of the identities of two European assassins, QJ/WIN and WI/ROUGE, and their use in the CIA’s assassination unit called ZR/RIFLE-Executive Action.

Do people think that it's just a coincidence that a known assassin and terrorist with a track record of such activities was in the city where and when the event happened?