Maybe this will come off as a bit cynical, but I do believe editors (as they are human) make mistakes on their end here and there. Some of the best people in the world got rejected, and you can attribute it to an (arguably sketchy) editor who didn’t give them the time and day.
I think the “prove them wrong” mentality has driven me up to this point to work toward being a better writer, if only for the satisfaction of silencing would-be critics.
Again, perhaps I am being cynical. To me, a lot of rejection letters are so impersonal.