“The premiere was a double-edged sword because I had been replaced by Mark during production. ...
“It [Brave] is still very much my film. But I think that is going to hurt always. It was very hard to believe what was happening (when I was replaced) and I never really got a straight answer as to why. It still haunts me today.”
It's never easy when you're pushed overboard. You emotionally hurt. You physically hurt. And it's not even like there's a "right" or a "wrong," a "just" or an "unjust."
It's just the way the corporate world ... and world in general ... works. Somebody has the power to make a change, so they make it. John Lasseter -- in this case, the person with the power -- felt there should be a new director on Brave, and he made it happen. From his perspective, bringing in Mr. Andrews was the right thing to do.
As to Brenda not getting a straight answer regarding why she was sacked? In my experience people seldom get the unvarnished truth. Nobody wants to be the bad guy. Nobody wants to be the bearer of bad news. It's the way dismissals usually go down*.
* Obviously there are exceptions to this rule, through not many. Much thanks to the people who brought the above piece to our attention.