Polls show that between 60% to 85% of the public over the decades believe in a conspiracy behind the assassination and reject the lone assassin explanation. It's been "the establishment" that has tried to tell them this didn't happen; it was one man with one rifle. The fact that we've been terribly served by the establishment (not as terribly as you think but that's another discussion) doesn't mean they are always wrong, must always be opposed. Sometimes they are right and the public wrong. As in this matter.
Second, you don't really think the conspiracy promoters will be dissuaded from their goofy ideas ("It was the CIA!" "No, it was the Pentagon!" "No, it was the Mob!" "No, it was anti-Castro Cubans!" "No, it was the Birchers!") with this release? When they are released and show nothing, what will the response be? Will it be any different than the one they gave with the previous releases? What is the usual response to conspiracy believers of any kind when the evidence contradicts their claims? Answer: "The lack of evidence is a conspiracy!"
It's a bit apples and oranges. While the establishment has generally supported a lone gunman conclusion because that is what the evidence demonstrates, they have not always been transparent with the underlying information. The FBI, CIA, and many other governmental agencies are secretive by nature and see no advantage in being transparent. That's why these files have still not been released even after 60 years. It takes an outsider like Trump to say enough is enough. Will every hard-core kook conspiracy theorist change their mind when the files are released? Of course not. Many of these people are mentally ill and invested in a JFK conspiracy. It does move the needle, however, with the average person who gives any thought to the case. I've had random discussions with folks who mostly couldn't care less about the JFK assassination, and many ask why the files haven't been released if there is nothing to hide. It's a reasonable question. Now that is done.
