OK, my job requires me to think outside of the box. So here goes.
The explanation requires two statements to lead it.
1. Baseball is much more similar to FP softball that Slow Pitch softball.
2. Slow Pitch softball is very different than FP Softball.
Let's take the look at two individuals and their background; a 30 year old male and a female of the same age.
23 years ago, the male started playing little league baseball and continue to play baseball through HS and possibly some college.
23 years ago, the female, if she played ball at all, would most likely have played slow pitch rec ball.
The experience factor would favor the male, ie. hitting, stealing - though somewhat different, fielding, strategies, coaching exposure, avid follower of the sport...etc. 99.99% of the women did not have this benefit.
15 years ago, there were still many schools that only offered Slow Pitch softball as a girl's sport. It was about this time that FP softball started it's run to overtake Slow Pitch in popularity. Back then, the majority of the FP pitching involved... "Who wants to try to pitch today?" It is nowhere near the level that you see today.
15 years ago, many of the males have already been in organized baseball for at least 8 years. They had the jump on the knowledge of the sports, etc. The conversion to FP was an adjustment of what they already knew, with the exception of pitching.
So the answer is, from that era, males have been better prepared to be a coach.
HOWEVER,
Present day FP programs, with teams starting at 8U or 10U will erase much of that deficit in the future and may tip the scales in favor of the females, eventually. BUT, It still goes back to what JoeA said, many women assume the role of a mother and leave the sport to care for the family, where - unfair as it is, males are more free to pursue coaching.