Well apart from F2F tournaments which have their own method of scoring, I would say that the objectives are really the choice of the individual player. I would say that it's roughly to maximize satisfaction in having played the game.
For most people, especially initially, that will probably come from winning the game, but this could change depending on how unrealistic that goal becomes or how eccentric the player is.
If winning becomes unlikely, players will likely shift their goal to getting a draw, surviving, helping out an ally or someone they like (perhaps for some meta-game exchange, like a date or a beer), or spiting an enemy.
Other objectives include trying not to tell a single lie, outdoing another player either out of spite or for reputation, trying to get the most meta-game benefit, making friends and socializing, getting a super long convoy, trying to tell only lies, forming tiny stalemate lines and hiding in the shell, etc.