Educated at elite British schools, he acquired a posh English accent and a fondness for fine tailoring. Unlike his onetime mentor, Mr. Mahathir, he did not have an instant rapport with the rural Malay Muslim base, and early in his political career he struggled to speak Malay.
Still, the legacies of Mr. Najib’s father, who was the second prime minister of Malaysia, and his uncle, who was the country’s third, helped make up for his lack of grass-roots appeal. In interviews, Mr. Najib was smooth, gracious and somewhat distant.
“Najib grew up thinking that leading the country was his birthright,” said Rafizi Ramli, a top strategist for the opposition that ousted Mr. Najib and the National Front coalition. “He doesn’t realize that you have to earn the people’s trust and maintain the people’s trust. He is completely removed from Malaysia, the real Malaysia.”
But his reputation was tarnished years before he became prime minister in 2009.
In 2006, when Mr. Najib was deputy prime minister, the Mongolian mistress of one of his advisers, Abdul Razak Baginda, was killed, blown up by military-grade explosives. Two of Mr. Najib’s bodyguards were eventually convicted in her murder.
French investigators are still examining whether Mr. Najib, during his time as defense minister, might have personally profited from around $130 million in kickbacks related to a transaction for French submarines. Before she was killed, the Mongolian woman, Altantuya Shaariibuu, claimed she was owed half a million dollars for brokering that deal.
The biggest scandal of all exploded in 2015 when opposition politicians and muckraking journalists questioned what had happened to billions of dollars that had disappeared from 1Malaysia Development Berhad, the country’s state investment fund.
Mr. Najib oversaw the fund, known as 1MDB, and unveiled it in 2009 as a surefire way to bring further prosperity to Malaysians through smart foreign investments and development projects.