To all the 'so what, noone died' brigade - regardless of the money and victims they fleeced, it is a big deal for the reader.
I read The Salt Path during lockdown at an incredibly difficult time in my life when I was going through a hideous ordeal. I found the book comforting and inspiring at the time (maybe because I was trapped indoors).
To find out she is not the person she said she was feels like a betrayal. Not a big one, obviously, but a betrayal nonetheless.
When we read memoir we feel a connection to the author, and put our trust in them. I write memoir too and it is big responsibility to tell the truth but also to be responsible for the people who read it.
She has pissed all over that trust. It may feel like nothing to all those people who never liked/believed the book anyway, but that doesn't mean it's not important.