I've always thought he was just terrible.
As great an individual talent as Lebron is, he needed a coach that could/would maintain team basketball. Celtic green-blooded Paul Silas tried that early in Lebron's career, suggesting after one game, when asked "what more can Lebron do?", that he could try to play defense. Obviously, he was fired.
Frankly, I thought the team did a decent job bringing in talent this year, but Brown did a terrible job integrating that talent with Lebron in a team offense.