U. S. Government lied about the JFK assassination. And the U. S. Government lied about the Roswell crash. The logical conclusion? The the government conspired to kill JFK? And conspired to hide the truth about Space Aliens? Possibly conspired not just among themselves but with the Space Aliens as well? Is this really true? No. People, and governments, tell lies for all sorts of reasons.
The term "Conspiracy Theory" was not invented in 1964. This term had been used for over one hundred years before the Kennedy assassination. It has been a term used to argue against the probability of Large-Secret-Enduring Conspiracies. A logical type of argument used by rational skeptics over the course of many generations before 1963. Large-Secret-Enduring conspiracies just naturally appeal to people, despite improbable nature of these theories, when some serious thought is given to them.
While it can be argued that a conspiracy to kill JFK does not need to be Large-Secret-Enduring, it could be Small-Secret-Enduring, the truth is that the average person who believes in a JFK conspiracy, envisions a Large-Secret-Enduring conspiracy. This is the notion that is pushed by supporters, like in the movie "JFK". People go "Ho-Hum" over Small-Secret-Enduring conspiracy theories, but not Large ones.