IF the "grew apart" line they are pushing is true, maybe Sue wanted Markus to become a responsible father and family man. Put away the spliffs, take out the ear plugs, leave the discord groups, stop playing so much vidya.
Markus thought he could have the best of both worlds; successful YouTube channel, playing Halo, drinking at clubs with his libertarian pals and have a doting wife who put up with his arrested development.
Sue's scorned lover approach, blindsiding Markus with the public announcement and stating that she would be looking after "[her] daughters" seems to suggest that she is pissed at him. Maybe the bussy theory holds some credence.