Complex sentence: One year prior to Bobby Manna's imprisonment Fiumara's old rival John DiGilio disappeared and was presumed dead, this clearly gave Fiumara greater underworld power and influence within the New Jersey rackets as two of his main rivals had been eliminated in some manner.
Split into simpler sentences: One year prior to Bobby Manna's imprisonment, Fiumara's old rival John DiGilio disappeared and was presumed dead. This clearly gave Fiumara greater underworld power and influence within the New Jersey rackets, as two of his main rivals had been eliminated in some manner.