It was late September 2014. The firm’s co-founder and chief investment officer — the brilliant but mercurial Bill Gross, known as the bond king for his decades-long streak of stellar returns — had abruptly resigned via a handwritten letter left at the firm’s offices in the middle of the night. Gross’s shocking exit capped months of mounting tensions at the firm. His heir apparent, PIMCO CEO Mohamed El-Erian, had resigned that January after openly arguing with Gross; other portfolio managers had threatened to walk if Gross wasn’t fired, according to press reports at the time.