Outgoing Rugby Australia chief executive Raelene Castle faced "unwarranted criticism" and social media "bullying", says chairman Paul McLean.
Castle resigned on Wednesday after the board lost confidence in her ability to take the game forward.
McLean said it was not a reaction to a letter sent by a group of ex-Wallaby captains, calling for new leadership.
He said a board decision "is not going to be a reaction to a small cohort".
Castle endured a turbulent two and a half years in the role, with Australian rugby union struggling on and off the field.
In 2019, Castle sacked Israel Folau after the full-back wrote homophobic posts on social media. Folau and RA later reached a settlement.
RA is braced for substantial losses because of the coronavirus pandemic and McLean added that a "lesser person" than Castle would have "thrown the towel in ages ago".
He said: "The board has had to consider how we take the game forward and that crystallised some of the thinking about whether Raelene was the right person to do that.
"I think in normal circumstances, without the things that have happened in the last two years and some of the unwarranted criticism and in fact bullying, I think it may have been a different scenario.
"But the board has to make a decision about how the game can progress, and if there was a clearer pathway to doing that then we needed to take that pathway because we represent and manage the whole of the game."
On the subject of "bullying", McLean added: "I'm not a social media person, but I'm aware of some of the things said over a period of time in a quite vicious and vitriolic way. The silent forces, the dark forces, those are the things that upset me most.
"The people that didn't know the facts, the faceless people out there, that was the damaging thing from her perspective and she shared some of that with me, which I found quite abhorrent."
McLean praised Castle's character and dignity throughout the process, saying she did everything in her power to make a success of the role.
"She would run through broken glass to get things done - and she has done that," he said.
"Her commitment has been extraordinary. She has worked 40 days straight. Her resilience and dedication is unquestioned and I am very grateful for what she has done in a very challenging time."
McLean played down the impact of a letter signed by 10 former Wallaby captains which said "the Australian game has lost its way" and called for new leadership at the top of the sport.
Nick Farr-Jones, the 1991 World Cup-winning skipper, was among the Australian greats to voice his concerns. McLean has urged the group to be part of the solution.
"I have had numerous conversations with Nick Farr-Jones," he added. "Let's be clear here: it's a very small collective of people who have been involved in the game of late.
"The significance of the group is probably the people who aren't on the list. It's great people who want to put their hands up and be involved, but they need to be part of the process."
With former head coach Michael Cheika released following Australia's quarter-final humbling at the hands of England at last year's World Cup, Castle recruited a strong coaching group to join in the summer, with the highly-rated Glasgow boss Dave Rennie replacing Cheika.