In the first one, you could drop in and out of each other’s games and you would share progress on relevant missions. In number 2 you would join one players game, only they would get credit for any progress and it tethered you together. So although technically co-op, it was a significant downgrade from the first game and didn’t lend itself to the open world nature of the game, more like being player 2.
I kinda assumed this was part of their plan. Rope along some Republicans who are too moderate(?) for Trump, then ditch at the last minute and tell them they have to vote for Trump now. Gives less chance that they’ll have time to sway to Dems or other 3rd party candidates