Abacha was a military dictator who ruled Nigeria from 1993 until his death in 1998. He was a highly controversial figure, and his rule was marked by widespread human rights abuses and corruption. In 1998, Abacha was found dead in his presidential palace in Abuja. The official cause of death was a heart attack, but there were many rumors that he had been assassinated.
Some of the evidence that supports the theory that Abacha was assassinated includes the fact that he was in relatively good health prior to his death, and that there were no signs of a struggle in his bedroom. Additionally, there were reports that several of Abacha's bodyguards were killed on the same night that he died.
The Nigerian government has never conducted a full investigation into Abacha's death, and it is unlikely that the truth will ever be known. However, the theory that he was assassinated remains a popular one among many Nigerians.