There were female warlords and rulers throughout history. Heck, the conqueror Cyrus was ultimately defeated by a female ruler. That said, they are not common place. I have no wish to get into why that may be, only that this is the case. Calradia is set in a fictional universe based on an historic time period on earth (ish), with fictional factions based on real world historical peoples.
I remember that after playing Warband for a while, I created my first female character and she was met with criticism by many male nobles in the game. I found this fascinating, and it made for great flavor in playing the game, even though the implementation was very limited and shallow. When I started playing Bannerlord, one of the first things I noticed was the preponderance of female warrior companions and warlords, and my first thought was this: "It's too bad they went this route, it was interesting to play as a female who had to fly against tradition." That dynamic is gone, sadly, and I was hoping they would not only keep it but add some depth to it.