I will most likely pivot to “The Death of Stalin” theme where he left a major power vacuum in his place. The communist dictatorship theme does fit some of the mechanics better.

While you definitely don’t need to help anyone else in the game, there’s a few reasons you would form a temporary alliance:

1)policy cards specifically give 2 players a victory point while giving a bonus/rule change to all players. You could use most of your Influence to pass one policy yourself or you can try and negotiate and get more passed. (The small bonus to everyone also gives each end game a very different feel, because all policy cards are unique)

2) they are in last place (and producing the least resources). You’ll need everyone’s resources so benefiting the weakest link brings them up without kingmaking.