OctavianF, Diplomacy is an awesome game if you play it properly.
Here are a few basic tenets to keep in mind for your future games:
1. No pre-arranged alliances. You can't enter a game with a group of friends with the idea of removing players who are not part of your group. Alliances must be formed in-game. If you are playing with friends you probably should announce this at the start of the game. Diplomacy is not a team game.
2. You can't play with more than one account. You are only allowed to have one account on webdiplomacy.
3. Play play to win, if you can't win play to draw, if you can win play to survive.
You broke principle 1, which made the game unfair from the outset.
It certainly looks like you may have had more than one account in that game, judging by at least one of the global chat messages.
Your allies broke principle 3. They were playing to help you win, even to the point of sacrificing themselves. For example Austria could have retreated to Venice instead of being eliminated.
As I said Diplomacy is not a team game. You can form alliances in game, but these must be flexible, and it is to be expected that these alliances will shift during the course of the game, as the balance of power changes, and as commonsense would indicate.
To help you see things from Bilbo's point of game. Would you join a game (by yourself) where you knew from the outset that the rest of the players were friends intended to play as a team and remove non-friends from the outset? I don't think so. What would be the point?
If you play a few more games here, without your friends, you will understand that what we are saying is right, and a much better way to play. You will also become a better player.
I suggest you check out the School of War thread. This might help you understand Diplomacy a little better.
Also check out the diplomacy archive. This website has some excellent strategy advice including various opening for the different powers.