Flori, in a sense, think about this.
You hid without doing WxW for 2 possible reasons, 1 being it's high risk to achieve this and attack because you might fall and die with fall damage, and the 2nd being avi may possibly fall during his next turn making it easy for you to attack, now, there is no rule stating you are not allowed to do this, although most people would look at it as being a bit of a cowards tactic.
Avi knocked you and killed you without doing WxW, for the same reason as it would be high risk to achieve it and attack without falling therefor probably losing the game, and as there is no rule about knocking a worm before collecting a crate or doing WxW, it would be a stupid thing to risk this, so he just done the fall damage and won the game.
Neither of you wanted to lose, both of you done something "lame" but legal to try and win, avi's "lame" but legal tactic worked better than yours, that's really all there is to it.
Couldn't you both just accept you were as bad (or good) as each other, and let this one slip?