I have a working theory the reason Trump has not been assassinated is actually because world leaders and powerful institutions recognise how laughably incompetent he is and do not want someone more qualified to fill the role of Dick-Tater.

I mean, a number of people have had a go at Trump.

https://en.wikipedia.org/wiki/Security_incidents_involving_Donald_Trump

On June 18, 2016, Trump was giving a speech at the Treasure Island Hotel and Casino in Las Vegas, Nevada, as part of his presidential campaign. During the speech, Michael Steven Sandford, a 20-year-old British man, attempted to grab a Las Vegas Metropolitan Police officer's pistol. The officer quickly subdued Sandford, who was arrested and handed over to the United States Secret Service, where he expressed his desire to murder Trump.

On September 6, 2017, in Mandan, North Dakota, Gregory Lee Leingang stole a forklift from an oil refinery and attempted to drive it toward the presidential motorcade while Trump was visiting to rally public support. After the forklift became jammed within the refinery, he fled on foot and was arrested by the pursuing police. While interviewed in detention, Leingang admitted his intent to murder the president by flipping the presidential limousine with the stolen forklift, to the surprise of authorities, who had assumed he was stealing the vehicle for personal use.

On July 13, 2024, Thomas Matthew Crooks fired shots into a Trump rally from an elevated position outside the venue while Trump was giving a speech near Butler, Pennsylvania.[15] Trump was injured and was bleeding from his right ear after the shooting.

On September 15, 2024, Ryan Wesley Routh was sighted bearing a rifle in shrubs at the Trump International Golf Club in West Palm Beach, Florida, while Donald Trump was golfing at the club. A Secret Service officer shot at Routh, who fled. The suspect was apprehended while driving away. The FBI was investigating it as an assassination attempt.

And then there are Iran's attempts:

On July 16, 2024, in the aftermath of the attempted assassination of Donald Trump, the United States Secret Service revealed details about an Iranian plot to assassinate Donald Trump.[338][339][340] Adrienne Watson, a spokesperson for the U.S. National Security Council, said that the plot was believed to be in revenge for the assassination of Qasem Soleimani...Three weeks later, on August 6, 2024, it was revealed that a Pakistani man with connections to Iran, Asif Merchant, tried to recruit people for the assignment, with one turning into an informant for the FBI. Merchant was arrested in Houston, Texas on July 12, just before attempting to leave the United States.

On November 8, 2024, the U.S. Department of Justice charged three men in connection with alleged Iran-linked murder-for-hire plots targeting high-profile U.S. citizens in a criminal complaint unsealed in New York. The suspects in the case are Farhad Shakeri, Carlisle Rivera, and Jonathan Loadholt. The FBI accuses Shakeri, an Afghan citizen of being an “asset” of Iran’s Islamic Revolutionary Guard Corps (IRGC) and is believed to be based in Tehran. Shakeri, who immigrated to the US as a child was deported in 2008 after spending 14 years in prison for a robbery conviction. The IRGC allegedly tasked Shakeri with orchestrating assassination plots as revenge for the killing of Soleimani. The intended targets included president-elect Donald Trump, an Iranian-American activist, and two Jewish-Americans residing in New York City. Rivera and Loadholt, who met Shakeri during their time in prison, were recruited to assist in these plans and have since been arrested, while Shakeri remains at large.

The two attempts to assassinate him with a rifle were pretty close. One guy sent rifle rounds very close to him, either hitting his ear with a round or with shrapnel, and I suspect that the other could have succeeded had some Secret Service guy not noticed the rifle barrel extending from the bush the guy was hiding in before the guy had the opportunity to take a shot.