Short answers, pulled from the story.
Mobutu Sese Seko, born Joseph-Désiré Mobutu on the 14th of October 1930, was the president of the Democratic Republic of the Congo from 1965 to 1971 and the first and only president of Zaire from 1971 to 1997. He ruled for more than three decades in total before being ousted by rebel forces in May 1997.
Estimates of Mobutu's personal fortune range from US$50 million to as high as US$5 billion, accumulated through corruption and the exploitation of Zaire's national resources. According to the Washington Post, he ranked as the third-most corrupt leader since 1984 and the most corrupt African leader during the same period. By 1970, it was estimated he had stolen 60% of the national budget for that year alone.
Mobutu's authenticité campaign, launched from 1966 onward, sought to purge colonial cultural influences from Zaire. He renamed cities, changing Léopoldville to Kinshasa and Stanleyville to Kisangani; renamed the country itself as Zaire in October 1971; banned Western attire in favour of an abacost tunic; and ordered citizens to replace European names with African ones. Priests who baptized a Zairian child with a European name faced five years' imprisonment.
The United States backed Mobutu primarily because of his fierce anti-communism during the Cold War. He served as a strategic counterweight to Soviet influence in Central Africa, and the US was the third largest donor of aid to Zaire after Belgium and France. When the Cold War ended and the Soviet Union collapsed, US support evaporated; in 1993, the State Department denied Mobutu a visa to visit Washington.
Mobutu seized power in a bloodless coup on the 24th of November 1965, exploiting a political paralysis after Parliament twice refused to confirm an anti-Tshombe prime minister-designate. He assumed sweeping executive powers under a state of exception, suspended Parliament by March 1966, and established the Popular Movement of the Revolution as the country's sole legal political party in 1967.
Mobutu's government transferred Patrice Lumumba to the rebelling State of Katanga on the 17th of January 1961. Lumumba was executed that same day by the secessionist forces of Moise Tshombe after being handed over by Mobutu's government. Mobutu had originally deposed Lumumba's democratically elected government in a coup on the 14th of September 1960, with the support of the United States and Belgium.