Fast forward to the late 90's & early 2000's when Voyager/Enterprise aired and the idea of a females in position of authority is pretty well accepted - so women have already been shown to command starships.
That could be the "in universe" explaination, Human society when through a period (however long) where women were simply not placed in positions of authority
, decades pass and society altered and women in charge of starships was acceptible.
Even today in 2013, for a women to be in command of a naval combatant is rare.
Which would seem odd as we've seen Number One as XO, Nancy Hedford as a Federation Commissioner, Areel Shaw as a prosecutor and even Lester herself as an expedition leader.