I won something! But then i dont?

Was it a public or private giveaway? If it was private, were there any special rules on the giveaway? The only way that should happen is a) you didn't meet the rules of a private giveaway and the creator asked for a reroll, b) there was something wrong with the giveaway itself (the creator didn't understand how the site worked, the creator selected the wrong game, etc.) and requested the giveaway be deleted, or c) you already owned more than half of the bundle and the creator requested a reroll.

Edit to add c).

I guess the GA creator rerolled it based on the "Majority of bundle exists in their account" reason.

Try to refrain from entering giveaways for packs if you already own the majority of the games contained within. The giveaway creator may request a new winner if you own a high percentage of the packaged games.

i didnt check your profile for dlc, but you do own JC2

Creator could have rerolled because you already have Just Cause 2, maybe?

Uh... i dont know. It was on normal "new" page and i just randomly entered like every other giveaway. other than that there was a button leading me to the page where they are selling it.

If the GA had already ended, there is no way for the gifter to delete the giveaway without the giftee's concern. My guess is the creator of the GA asked for a reroll because OP already owns Just Cause 2 in their acc, and especially if the giveaway creator specifically asked not to enter if users already owned a game from the bundle.

Sanic pls, what did u do