Spoilers (I guess)
Ultimately (Marcus special) it boils down to some extremely meta bs about the world not being real and everything being subject to change.
End spoilers
Personally I didn't find the endings in any way satisfying.
That aside, no, no happy endings - I think MC being the new leader of LA mosquitoes is as high as it gets. So don't break your back trying to find fault within your play style.
Indeed, there are 4 endings (Saorise, Randal, Andrei, MC being the new ruler), and without spoiling things, you need to see how your LI ends up acting in different situations to get "special" endings (emphasis on Sao and Randal).