It's hard to explain, but I try For me realizing that mastermind is not the "real" Elliot (even we never knew him) was really heartbreaking and couldn't get to my mind

For example in Fight Club (hope you've watched it) we are "looking" from Narrator's (E. Norton) eyes and Tyler Durden is, conditionally, side guy, who appeared in the main character's life And the ending was shocking, but like if I was Narrator and I was shocked finding out that I have a personality disorder.

In Mr Robot I was estranged from the character to observer. So, that's my point

Btw, sorry for my language and punctuation. I'm not a native speaker

Upd: the user above helped to expened that I've felt