i dont really think that MBTI types has anything to do with masculinity
I agree with your premise, but by agreeing, I also find it necessary to discover the meaning and reasoning behind Steele's premise.
I do not remember the exact statistics, but males are approximately:
67% thinker
75% extravert (also true for females)
75% sensor (also true for females).
This means:
50% of males are ST.
37% of males are EST.
This may lead one to question whether EST's or ST's create the norm.
A more convincing way of putting it is that
most males prefer extraversion,
most males prefer sensing, and
most males prefer thinking.
Or perhaps a functional way of putting it might be: most males have dominant/secondary Si Se Ti Te. And perhaps because the Extraverts are predominant, it is likely that
dominant Se and Te are the norm. Hence EST.
The "ideal", according to Steele, is thus seen from the perspective of who the majority are.
And why ESTJ instead of ESTP? It is because ESTJ is seen as a more capable leader of a family or social unit, perhaps?