The HSCA concluded that there probably was a conspiracy.
National Security insiders from RFK to John Kerry speculated that Oswald didn't act alone.
The US government now admits that UFOs are real.
US Report Can't Explain UFOs, But Says They're Likely Real and Possibly a National Security Threat
https://www.military.com/daily-news/2021/06/25/us-report-cant-explain-ufos-says-theyre-likely-real-and-possibly-national-security-threat.html
"The report gives no indication the UAPs' [unidentified aerial phenomena] origins are extraterrestrial."
There's a difference between acknowledging UFOs as "unidentified" (the government has records of unidentified aerial phenomena going back to the 1940s) and then taking the final step based on "gut feeling" that they're from other planets.
Same with the "conspiracy" indications coming in the weekend of the Katzenbach memo. A "communist conspiracy" the Dallas police were pulling out of their ass and the "right-wing conspiracy" the Soviet press were pulling out of their ass. There was the fear that a political-based Congressional Committee would invent and parade a "communist conspiracy" by way of McCarthyism. When Katzenbach wrote his memo, there was no reason for high-up law enforcement and justice department officials to take the next step based on "gut feeling" and declare such "conspiracy" claims were legitimate especially when all the evidence being gathered pointed exclusively to Oswald's sole guilt.
If there should have developed evidence of equal credibility that Oswald had mysterious associates who, for example, had funded him, or supplied the rifle, or drove him to work that morning, then that would be in "a complete and thorough FBI report on Oswald and the assassination" and added to "all the facts will be made public property in an orderly and responsible way".
"Because for the very simple reason, if that was not a fact, and
all the facts were not on the table, then it seemed to me that
nobody was going to be satisfied, and I thought that the public
was entitled – if there was a conspiracy, then we ought to say
there was a conspiracy. If there were confederates at large,
it ought to be said there were confederates at large. I knew then
already that Oswald had been in Russia, Oswald had been in
Mexico. Now, if you are going to conclude, as the Bureau was
concluding that this was not part of a conspiracy, that there were
no confederates, then you had to make that case, with all of the
facts, absolutely persuasive. If you didn’t reveal these facts,
somebody else was going to reveal them. Now, if there was a
conspiracy, there was a conspiracy, and you put those facts out.
But if you were persuaded Oswald was a lone killer, you had
better put all of the facts out and you better not cover up anything,
and you better say now all of the facts are going to be made public.
That was the advice I was giving Moyers and that was the advice
I was giving the President and that was the motivation for the
Warren Commission. I don’t think this is artistically phrased.
Perhaps you have never written anything that you would like to
write better afterwards, Congressman, but I have."
— Nicholas Katzenbach, to HSCA