The way aui reacted shows that EG immensely mishandled the situation, regardless of who is right or wrong.
Like I said before, fear is extremely versatile and will have no problem playing 4 but it will take some time for him to get as good at the role as aui. Milk is right, dota overall level has improved by a huge margin and while fear is a monstrous player, aui has shown time and time again that he is one the best 4s in the world.
I agree with tobear, the move was probably decided before TI. I think the timing of the announcement is perfect, it was just handled very poorly, especially if the rumors about the team not discussing this with aui face to face are true.
From an esports perspective, I think the decision is a good one. I think EG gain more by getting RTZ and keeping fear than what they lose by kicking AUI (as good of a player as he is). This might affect their overall level in the next few weeks but ultimately, I think the team will be stronger with this lineup if they stick and practice together.
One last thing, Aui is sadly a very underrated player in my opinion. One just has to look at the recent facts. C9 is performing far worse since he left the team and EG won TI since he joined. He plays in a position where it is more difficult to notice his impact so I guess it's understandable. Very rarely will a support be under the spot light, unless you are FY rubick, it's the nature of the role.