Maybe you should consider adding some kind of an agreement at the beginning of the game, that it is not allowed to buy someone's city state and attack him at the same turn.
You should have probably voted for the player with the most votes that didn't go Autocracy, hoping that your combined efforts will keep that proposal down. Not sure it would have made a difference in the end but it's still sound logic.
Maybe you should consider adding some kind of an agreement at the beginning of the game, that it is not allowed to buy someone's city state and attack him at the same turn.
You should have probably voted for the player with the most votes that didn't go Autocracy, hoping that your combined efforts will keep that proposal down. Not sure it would have made a difference in the end but it's still sound logic.