The mystery over why an Army Special Forces soldier detonated a Cybertruck outside the Trump Las Vegas hotel on New Year’s Day has only deepened with the final investigative report released by cops Monday.

The 70-page Las Vegas Metropolitan Police post-crime dossier confirmed that Matthew Livelsberger, a 37-year-old active member of the elite Green Berets, left a “manifesto” on his phone, although the Department of War has deemed it classified and will not release it.

Livelsberger — known in the Army as a “Rambo-type patriot” — loaded up the rented truck with fireworks, gas tanks and camping fuel before detonating it outside the lobby of the Trump property on the Vegas strip.

The attacker, believed to have been a staunch Trump supporter, “simultaneously” shot himself as the truck began to burn, authorities said.

The blast injured six people inside the hotel.

Despite the War Department’s decision to keep Livelsberger’s manifesto under wraps, the LVMPD report references several clues about his motives.

He left behind a note claiming the attack wasn’t terror-related but a way for the solider to “cleanse” his mind — while blasting the “feckless leadership” of a US that is “near collapse,” authorities said.

“This was not a terrorist attack, it was a wake up call,” Livelsberger wrote in a notes app. “Americans only pay attention to spectacles and violence. What better way to get my point across than a stunt with fireworks and explosives.”

One of the attacker’s notes was sent to Shawn Ryan, a former Navy SEAL and CIA contractor. It has not been released in its entirety.

The local cops’ report calls the explosion “a premeditated attack involving a vehicle-borne improvised explosive device, with the potential to cause mass casualties and extensive structural damage.”

Livelsberger had served in the Army since 2006 and in Afghanistan in 2009. He was on leave from assignment in Germany at the time.

His wife had dumped him six days before over an argument about his apparent infidelity, prompting him to leave his Colorado Springs home the day after Christmas, two sources familiar with the investigation told The Post in January.

His wife — who had a baby daughter with Livelsberger — reportedly told him that she knew he had been cheating, sources said.

After leaving Colorado, Livelsberger rented the Cybertruck through the Turo app and made his way to Vegas, LVMPD said.

The FBI had been investigating whether Livelsberger’s target — the iconic hotel that bears the name of President Donald Trump — had been politically motivated.

LVMPD officials have claimed they have no control over the release of the contents of Livelsberger’s manifesto.

“The Department of Defense has exercised control over the manifesto,” the department told the Las Vegas Review-Journal.

The local cops claimed, “[T]he manifesto does not record any public business and thus is not a public record. Instead, it is evidence collected by law enforcement pursuant to an investigation.”

Their own after-action report details the police response and ensuing investigation from several agencies, including the US Army Criminal Investigations Division, Bureau of Alcohol, Tobacco, Firearms and Explosives and the FBI.