Complex sentence: Gotti, by then the most targeted criminal in the country, came to share the assessment amid mounting investigative pressure and costly blunders by the inveterately indiscreet Ruggiero, who had completely fallen from favour by the time of his death in prison.
Split into simpler sentences: Gotti, by then the most targeted criminal in the country, came to share the assessment amid mounting investigative pressure and costly blunders by inveterately indiscreet Ruggiero. He had completely fallen from from favour by the time of his death in prison.