According to the novelization she did it to protect his career so he would not get into trouble for what happened.
Really. Hmm. I wonder if it worked.
Even if Uhura left behind a sworn statement that she alone was at fault (and testified to that effect at trial - in fact, every one of them was witness to Mr. Adventure protesting "No orders? No encoded IDs?"), would Starfleet believe it? I'm guessing there's some kind of log of every command executed at that station, complete with a record of who performed it, so there'd be "proof" that all of the transporting was done by Uhura alone, but still...I wonder if this guy faced a court-martial for this. We know that the rest of them did.
Edit: Memory Beta says that Mr. Adventure appeared in the novel
Catalyst of Sorrows (in which he is named 'Scott Heisenberg'). Anyone read that? What happened to him?