Seinfeld normalised the weak willed, feminized man.
It made it all acceptable.
Seinfeld the most successful pop culture psyops of its time, and it's not even close.
Discussion
They were already that way by the time Seinfeld came out, that's why it resonated so well.
They definitely tapped into the uncertainty that men felt at the time.
It gave them permission to be pussies & chase meaningless casual sex.
It normalised the shift that was already starting to occur.