Complex sentence: Genovese's actions during his time as boss are widely regarded as major causes of the rapid decline of the American Mafia's power: from several highly-publicized murder trials, to his incompetence towards the Apalachin Conference in 1957, and numerous other mishaps.
Split into simpler sentences: Genovese's actions during his time as boss are widely believed to be major causes of the rapid decline of the American Mafia's power. Amongst these are several highly-publicized murder trials, his incompetence towards the Apalachin Conference in 1957, and numerous other mishaps.