"Why?" is the obvious question, as the article makes clear for some reason the Feds went along with targeting these men (who were also members of the Nation of Islam. In Harlem? Not clear.) when the obvious pointed to Bradley at the Newark Nation of Islam mosque (the same mosque as the confessed third man, who identified him as one of his accomplices) they knew these things but they did not tell New York?!

But Mr. Greene’s description matched another man, one whose name jurors did not hear: William Bradley, a member of the same Nation of Islam mosque in Newark, N.J., as Mr. Halim. Mr. Bradley was an enforcer for the Nation of Islam, which Malcolm X had joined in 1952 and promoted unceasingly for a dozen years before an acrimonious break the year before the assassination.

He was less than six feet tall, weighed 182 pounds and was dark-skinned. He had been a machine-gunner in the Marine Corps and his criminal history included a charge of possessing an illegal weapon.

The description of Mr. Bradley was in F.B.I. files at the time, and Mr. Halim even identified him as one of the assassins. And the authorities were aware that the Nation of Islam was targeting Malcolm X; a week before the assassination, his house was firebombed while he slept inside with his wife and daughters.

And when Mr. Halim, also known as Talmadge Hayer, took the stand for the second time during the trial and confessed, he insisted that his two co-defendants were innocent.

And why did these 10 people say this? That's a lot of mistaken witnesses! Very odd, like mass hysteria.

At the trial in 1966, prosecutors cast Mr. Islam, who was once Malcolm X’s driver, as the assassin who fired the fatal shotgun blast. Mr. Halim and Mr. Aziz were said to have followed close behind, firing their pistols. Ten eyewitnesses said they had seen Mr. Islam, Mr. Aziz or both.

But the witness statements were contradictory, and no physical evidence tied Mr. Aziz or Mr. Islam to the murder, or even the crime scene. Both men offered credible alibis, which were backed by testimony from their spouses and friends.

also noted 

Mr. Vance’s investigators, working with Mr. Islam and Mr. Aziz’s lawyers, examined the evidence that had long been laid out and pored over publicly, including the F.B.I. file on Mr. Bradley. (Mr. Bradley, who changed his name to Al-Mustafa Shabazz, died in 2018 and his lawyer denied that he had participated in the murder.)

but so obvious a suspect, with a job like this, and the confessed Halim pointed to him as an accomplice! and after the firebombing of Malcolm X's home yet!

Years after the assassination, scholars suggested William Bradley, an enforcer for a Nation of Islam mosque in Newark, was likely the man who fired the fatal shotgun blast.Credit...East Orange Police Department

[edit to fix blockquoting] 

Malcolm X's daughter found dead in her Brooklyn home on Monday: