Men who married women that had children from previous relationships had previously been viewed as fairly normal, good men who just happened to be marrying a woman that had kids. There's always a several media and cultural tropes that paint these men in a positive light, as the man who took on the responsibility to take care of children who didn't have a father. Of course, there are also stereotypes of the abusive stepfather, but the role was rarely viewed as the pathetic position many young men view it today. Even historically, George Washington was a stepfather, and Joseph is Jesus's stepfather, as was many other individuals in history, but they aren't viewed with the derision that exists today.

At some point in the 2010's there seemed to have been a shift in attitudes for those under 30 (maybe under 40 as well), where becoming a stepfather/dating a single mom is now viewed as pathetic and bordering on cuckoldry. Single moms are verbally abused online and described as "bottom of the barrel" when it comes to dating. Even a beautiful woman on dating apps would be passed over for a serious relationship by a significant percentage of young men if she had a child.

Of course there is the commonly expressed view of "beta bucks", but these views aren't limited to just men in TRP communities. They are expressed in almost all subcultures that young men frequent. It's form of dehumanization for everyone involved; the stepdad/boyfriend, the mom, and the kids are all stereotyped into the worst possible versions of these roles.

I'm not asking those here why they wouldn't date a single mom, I am asking what caused this societal shift to occur? What led to the spread of these beliefs? Or do you disagree with the premise, have these attitudes always been this common?

(My perspective is that of a man in his mid-twenties.)