If you mean "we" as in the Tarnished, we only killed him to stop his 'DYNASTYYY' from being formed. If you mean "we" as in the Elden Ring playerbase, Mohg was just playing the game of trying to become Lord (same thing the player does), there's nothing inherently wrong with what we thought he did at the time, since... When compared to what everyone else in the lands between did, kidnapping 1 dude and killing a few Tarnished (via the Bloody Fingers) is not exactly a massive sin.
