I had to look it up - Certified Registered Nurse Anesthetist.
https://en.wikipedia.org/wiki/Men_in_nursing
So male registered nurses in the US appear to be a solid single digit in terms of percentage. Wikipedia says 6.6%.
The internet says CRNAs are 41-43% male.
So a very small number of male nurses, and a majority of them becoming CRNAs, and so the average pay for male nurses is higher than the female average. But really, I bet the 59% female CRNAs are being paid the same.
This is the problem with looking at averages only. If men are being prefered over women in the CRNA program, there is a problem. If female CRNAs are paid less on average than male CRNAs there is a problem. But the average alone tells you nothing. It definitely doesn't give you enough information to show you which part needs fixing.