Leon Black plans to step down as chief executive of Apollo Global Management Inc. after an unconventional review uncovered larger-than-anticipated payments to dishonoured financier Jeffrey Epstein that it nevertheless was considered justified.The monthslong review by Dechert LLP found no ties that Mr. Black was involved in the criminal activities of the late Epstein, who was indicted in 2019 on federal sex-trafficking charges involving underage girls, according to the law firm’s report, which was disclosed in the securities filing Monday. In its report, Dechert found the costs that the billionaire had paid Epstein were for legitimate advice-on trust-and estate-tax planning that proved to be remarkable value to Mr. Black and his family. Mr. Black paid Epstein a total of $148 million, plus a $10 million donation to his charity-much more than was previously known.Mr. Black wrote in a letter to Apollo’s fund investors that he would give up the role of CEO to co-founder Marc Rowan on or before his 70th birthday on July 31 while retaining the role of chairman. In the letter, which was also disclosed in the securities filing, Mr. Black detailed other governance changes he is recommending to the board, including the appointment of more independent directors and the elimination of Apollo’s dual-class share structure.