That's basically what it is. Computers didn't come into their own as a "Thinkerer" field until the early 80s. By that time, most degrees had gone to women, and you were still seeing that population into the early 90s.
The shift in degrees occurred early/mid-80s with the release of the PC platform and Home computers, these things don't happen in the span of a few days. It takes years to change a trend like that in emerging fields. In the 90s, when I did my Comp Sci classes, we had like 80% of our teachers being women, while 90% of the class were guys.
Why is it so hard to accept that maybe women in general don't prefer the field, just like men in general don't prefer nursing ?
Huh? Women didn't get most of the degrees in the 80's. It was still very much a male dominated field, just not nearly so much so as it is today. In the 80's I had one female CompSci professor. The rest were all men.
The PC platform brought computing to the masses but it didn't fundamentally change what it meant to be a programmer or the skills that were required. It may have helped promote the start-up mentality of ridiculously long hours that are good for neither men or women.
Men tend not to go into nursing because there is a stigma associated with being a male nurse, - though that is changing and there are more men going into nursing than have in the past. And since there is a shortage of nurses (my wife is a nurse), men are getting actively recruited to enter the field.
I suspect a stigma is also why some women stay away from computer careers, - there's a nerdy image associated with it. It's not because they can't do the work or wouldn't enjoy it. History has shown that not to be the case.