EV = expected value, that is, one should strive for maximizing their diplomacy points. If you win, you gain more points than for a draw, thus winning is more desirable (from that point of view), but a draw is better than loosing your bet altogether. Also, I see this goal as a single one for each player (based on the rules) - and this were we drift apart fast. Many people will stick to their allies to the death and cannot be turned, because of good alliances, alliances in the future, bla bla - you get the idea. I do not like that, because it contradicts the maximizing principle (unless it favors me, of course).
For having fun - I admit right from the start that I like winning, or maximizing my points (within the rules, though, because this is the idea). I feel more satisfied when I got a win than when I lose. I still enjoy playing, but I enjoy the battle rsp. the struggle of 7 players to maximize their points and do everything in the rules to achieve it. This isn't always the case, I sometimes also play against someone due to a grudge because he called me names in private chat etc pp (I am human, I fall illogical behavior all the time after all). But I like the games where I see that is most cutthroat.
If you convinced your opponent to give you the win, than you adhered to maximizing your points. The other failed at doing so. So you played a better game of diplomacy and the other played a worse one - for my standards, at least.
Maximizing EV and that a perfect diplomacy game will lend in a draw are no contradictions, quite to the contrary. A fair game should always result in a draw, or an EV=0 for all participating players, if all the players play a perfect game. This is the bone of a fair game. But neither do we know it (I doubt it with Austria and Italy in diplomacy anyway), nor do we play perfectly at any time.
I also would doubt to call the creator of the game the master of it - you can have a good idea, but then some people can create a bigger understanding of the game by also consuming what others know and go deeper and deeper. Compare with chess, go et al.