There are likely several reasons:
Her tranifesto could expose how government professionals failed to address clear warnings from her.
Her tranifesto could expose her hatred of her Caucasian self because of what she was taught in school and in the Propaganda Media.
Her tranifesto could expose that her Gender Dysphoria, instead of being treated, was used as a weapon against her.
Her thoughts and actions destroy the Left's lie that mass shootings are the purvey of white males when the truth is that it's black males by far. She apparently wanted to be male and hated white people (despite being white), so not only did she hope to change her gender, she apparently wanted to change her race as well.
The tranifesto will show just how young adults who are mentally ill will are used as pawns to further the Left's agenda.