In announcing his resignation Mr Weldon said "the personal cost is now too high to continue in this role".
MediaWorks, the parent company of TV3 and RadioLive, said the board respected his decision, with chairman Rod McGeoch thanking him for his "success in driving change through the entire organisation and under his leadership MediaWorks has truly become an integrated company. Mark has agreed to assist the board on strategic projects and we would like to thank him for his efforts and successes."
Reaction to the controversial boss's resignation flooded social media. Former weekend newsreader Carolyn Robinson tweeted: "Goodbye Weldon. Don't trip on the ruins you created as you leave." Former Campbell Live producer Pip Keane posted: "It's definitely a karma day."
Mr Jennings said the cultural disconnect existed across the business from television into its digital and radio units. He said the MediaWorks business was often described as a "family" - a term he didn't personally like - but it was "a highly supportive culture and it's based on team work not individualism".
"People work very much for each other. That seemed to be very different to the way Mark saw things."
Mr Jennings said it had been difficult to be at the company during its transition - he oversaw many of the changes in news and current affairs.
The impact on him was the diminishing team spirit in the company as the culture changed. "The culture was a no blame culture. If something did go wrong we all accepted responsibility for it. It wasn't a culture to single people out.
"It meant we were close and people were always prepared to go over and above what they were paid for and what was expected of them. The hard thing for me was to see people drop off that."
He said media was a difficult industry in which to be working. Worldwide, media companies have been hit by technology changes that undermined basic business models.
"People were coming back to the company working at 100 per cent rather than 120 per cent and that extra 20 per cent is what gave 3News and other parts of the company an edge, and it also gave an incredible esprit de corp."
The main focus on departures from the company had been on public faces but Mr Jennings said staff had left from right across the business. "I don't know that news was put under more pressure than other parts. There was a perception that news wasn't as supported as it had been."
However, he said the contrast had to be seen against previous chief executives who saw news as a core strength of MediaWorks' offering.
"I think Mark just saw it in the same way as other parts of the company."
While MediaWorks was a private company, its role in media meant it had a responsibility to be open about its business with the public, he said.
"If you are in the news media business you are a part of the democracy of this country and people expect you to be open and play a role in New Zealand society."
Dr Cathy Strong, senior journalism lecturer at Massey University said Weldon's departure was "really good news for journalism".
"It actually means that MediaWorks now has the opportunity to bring in someone with the leadership skills to rebuild the TV3 news brand that has been so badly damaged. The flood of comments on social media shows that the purge of solid journalism was not acceptable to the New Zealand public and the direction Mark Weldon was taking the company had little support. Whoever takes over may find it difficult to attract good journalists back, as the embedded news culture has been decimated."
She said Hilary Barry's resignation last week was the last straw and Weldon's departure was inevitable "as he was running out of journalists to present with a red rose".
"Who knows what has been going on behind the scenes, but clearly someone with power has seen the way public opinion has been heading over the past year and realised it was untenable. My hat goes off to that person."
