Because making mistakes can lead to all kinds of shenanigans. Plus her in the moment writing is more relate able. Shes just the best. Her writing can stand for itself. Plus she has one of the best pony designs in the show, and shes super strong. Shes also a leader.
Because every time she makes a mistake she goes back in time and she fixes it. Nopony is ever the wiser. Well, except Discord, of course, but he honestly doesn’t really care so long as things stay interesting.
Perfect murdery?
Edited