In the early 80s when home systems like the C64 and TRS-80 were hitting the market they were marketed, essentially, as toys for boys.
I've seen a lot of advertisements for the Commodore 64 and don't recall any gender bias. Here is an example of the ads I remember:
https://www.youtube.com/watch?v=vLwTLpGzBB4
After begging my parents for months, I was given a Commodore 64 for Christmas in 1982 when I was 10 years old. My two sisters never had any interest in it despite my constant attempts to get them to use it with me.
Okay, but you're one person offering an anecdote. We are going to need better than that for a discussion about a cultural movement.
That also applies to the GP's assertion that the computers were gender biased in their marketing.
Somehow I doubt anyone here is going to do a quantitative analysis of 80's advertising...
So people bought them for their kids.
Their male kids.
Fast forward 10 years and the comp sci demographics shift.