So the only way the no confidence vote to hit over 3/4 with 3 already leaving would have had 3 added (to get to twelve) and hope all of them voted to keep it going? Does that sound right? OA MoC and MH maybe? Were there even any other IS factions of over a dozen worlds or the Equivalent? Maybe the mercenary board and the restaurant chain FFF? 
It's not "Roberts Rules of Order", and someone already pointed out; Most of the outcomes are plot decided, so anything and everything can and will be bent to make the chosen plot event occur, to include fictional rules of order and/or talleys that shouldn't make sense without large amounts of gymnastics to make them work.
For example previously, the Federated Commonwealth decided to have a massive, bloody civil war in the middle of an invasion that's already swallowed 40% of the Lyran member state's planets, including most of the industrial parts.
Before that, a secessionist sister-of-the-prince walks off with the Lyran state, only to turn around and make herself a princess on New Avalon.
Concurrent to that, the Lyrans, with an enemy on their SOIL that extensively uses battlearmor, spent vast amounts of industrial capital on a support weapon that's only good for slaughtering unarmored civilians and burning down villages. (They had to retcon that to give it SOME anti-armor capability after this was repeatedly pointed out in these and other forums with mockery and laughter.)
The Lyrans also invested heavily in quads while the invading enemy had omni tech and superior weapons ranges, and the initial heavy gauss rifle, which couldnt' be reliably fired on a bipedal chassis without putting said chassis on its ass. (and the main shot loses damage and velocity at long range because the projectile's got the aerodynamics of a perpendicular cube.)
IOW they concentrated the bad ideas, and the dumb ideas, to drive the plot results they needed for the plot.
Okay, now extend to the Star League. Sun Tzu in five years outmaneuvered
everybody. full stop. How does he cap this? by painting the Capcon a shade of "Easy Target", then counting on everyone else to do exactly the wrong thing for their own interests (but the exact right thing-besides Word of Blake, for his.)
and they did it.
I could see the walkaways happening in the aftermath of a vote refusing SLDF relief in the war torn former fedcom, or if Yvonne couldn't get financial aid for recovery, but Peter going along with it is nothing but pure plot-driven stupid juice. His situation he'd NEED the foreign aid and foreign
Trade to rebuild given that the Lyran state has been everybody's favorite battlefield since 3049.
Including his family members, who pitted their key units against their key units in a fratricidal festival of idiocracy, mismanagement, absent landlordism, and raw stinking hubristic stupidity (From 3062 to 3067, no less. He had to kill his great aunt to stop it.)
but without the overriding plot drive, the actions don't make sense the same way using 600 steps to complete a movement that only needs 6 doesn't make sense.
Clearly someone should've been checking the royal apartments for leaded glass windows and flaking lead paint back in the 3030s, when the children were small.
when forty percent of your nation is occupied and all you've got is a lousy cease-fire the other side's already broken twice? you don't abandon your alliances, you
beg them for help.
this common sense was not followed, because if it HAD been, the Republic of the Sphere could never be born, and nobody would be owing Devlin Stone a ****** thing.
The PLOT required the outcome of the vote being dissolution.
In the middle of an invasion that was only on 'pause'.
