It was all Charles Moulton (pen name of psychologist William Moulton Marston). Here's a brief article touching on his ideas in that regard.
A couple of quotes:
Through his psychological research, Marston had come to the conclusion that women were naturally superior to men, both morally and in terms of skill. Further, he believed that women’s tendency toward loving submission was far preferable to masculine authority, which he viewed as toxic and violent.
Additionally, the goal of the much-vaunted bondage imagery that pervaded Marston’s stories was two-fold: first, to serve as a metaphor for the oppression women suffer in patriarchal society, and second, to add an erotic element so that young readers found themselves associating submission with love, through what Marston called “sex love training.”
And another profile from The Atlantic:
And in almost every issue, she is chained or tied up. This plot staple provoked debate from the start: opponents of comic books thought it smacked of sexual fetishism (and fetishists agreed). But whatever it represented in Marston’s personal psychology, bondage was an obvious metaphor for the many ways in which women were collectively and individually constrained by law and “tied down” by marriage, domesticity, children, and all the rest of it.