Temporal Investigations forced it through.
People keep asking where the timecops were to stop Admiral Janeway?
I say pishaw! Where were the 29th century time cops that helps Admiral Janeway push her mission through to fruition?
Her backstep was authorized by whoever controlled time upstream.
Temporal Investigations take orders from the future.
They'd be fools not to if they could trust the future, but they can't, so should they?.
Only Kim wouldn't blow Kathryn out of space when she is being so untimely irresponsible disposing of a bad future history that no long has the will to persist and replacing it with the future we've come to expect as a glorious destiny.
Janeway is a patsy and Kim is a fluffer at the half way mark.