Mr Maxwell, who did not return calls for comment, started in television at TVNZ in 1988. He went on to run his own production company, Te Aratai Productions. He rejoined TVNZ in 2008 in the executive role overseeing Maori programming. Mr Maxwell was also a member of Te Putahi Paaho, the Maori Electoral College which set up the Maori Television Service.
He was known to be close to board chairwoman and former National Party MP Georgina Te Heu Heu. She did not return calls for comment.
Film-maker Tainui Stephens paid tribute to Mr Mather's leadership at Maori Television. He said he had debunked criticism which dogged the channel when it started in 2004.
Mr Mather's style of leadership had grown the station's kaupapa and delivered to its audience since he took over, said Mr Stephens, Maori advisor to New Zealand On Air.
"Jim Mather is fond of saying 'where others zig, Maori Television will zag'. There is an advantage to being a smaller operator.'
Mr Stephens said Maori Television now managed the difficult job of serving the needs of the Maori language while meeting the wider community's interest in the channel.