Complex sentence: In September 1999, Byrne stepped in as CEO after Brazell refused to kowtow to what appeared to some to be Byrne's narcissistic personality disorder, and renamed the company "Overstock".
Split into simpler sentences: In September 1999, Byrne stepped in as CEO. Regardless, the change was made, and shortly after assuming the CEO role, Byrne renamed the company "Overstock".