It would seem that completing the synthetic ascension path makes it all but impossible for your nation to embrace any faction other than the materialist faction. The reason for this is that, firstly, robotic pops and AI rights boost materialism attraction; and secondly, all robotic pops are able to join the materialist faction irrespective of their personal ethics.
In my current game, I'm attempting to engineer a shift from pacifist governing ethics to militarist governing ethics. Pacifism attraction is down to 5%, and 15% of my population is pacifist. Militarist attraction is 27%, and 22% of my population is militarist. However, only 6% of my population is in the militarist faction, preventing me from embracing it. Materialist attraction is 37%, 25% of the population is materialist, and a whopping 81% of my population is in the materialist faction. Robot pops are in fact (at least) twice as likely to join the materialist faction as they are to join any other faction. This is mental.
In my current game, I'm attempting to engineer a shift from pacifist governing ethics to militarist governing ethics. Pacifism attraction is down to 5%, and 15% of my population is pacifist. Militarist attraction is 27%, and 22% of my population is militarist. However, only 6% of my population is in the militarist faction, preventing me from embracing it. Materialist attraction is 37%, 25% of the population is materialist, and a whopping 81% of my population is in the materialist faction. Robot pops are in fact (at least) twice as likely to join the materialist faction as they are to join any other faction. This is mental.