As Mr. Trump focused increasingly on Georgia, a state he lost narrowly to Mr. Biden, he complained to Justice Department leaders that the U.S. attorney in Atlanta, Byung J. Pak, was not trying to find evidence for false election claims pushed by Mr. Trump’s lawyer Rudolph W. Giuliani and others. Mr. Donoghue warned Mr. Pak that the president was now fixated on his office, and that it might not be tenable for him to continue to lead it, according to two people familiar with the conversation.That conversation and Mr. Trump’s efforts to pressure Georgia’s Republican secretary of state to “find” him votes compelled Mr. Pak to abruptly resign this month.