I don't have an answer, I can only offer my opinion:
As I understand he did all that just to get popular so he could be a part of collaborations, maybe push his own projects through the portal easier, get higher score, etc. So, he submitted ~9 stolen animations, then 2 animations of his own (I mean those two left on his account),.. and a few days later he submitted a stolen animation again, I don't understand his logic. By the way he did all that in a period of ~3 months, that's like one submission per week, pretty fast huh? (and suspicious) :)
Now about the tear and the Oasis Collab. My first guess is that tear was removed because jack-skeelington could not provide the .fla, but,.. it was removed two days after the confession, which probably means that someone recognized the real author, or an admin was on submission deletion spree. :)
I couldn't find the Oasis Collab, but I found another collaborative flash called Burn Baby Burn, jack-skeelington is listed as a co-author in the author's comment box only, although in 2004 that animation was in the list of his submissions. Also notice jack-skeelington's animation style it looks similar to the one he used in NG Horror Show.
I assume that the co-authors of NG Horror Show saw jack-skeelington's .fla, so that one should be ok.
And Grey In Grey is also ok, because jack-skeelington only helped with the graphics.
I guess that an admin removed all his solo projects with one click, but he couldn't touch the collaborative flashes because it would be unfair to remove a hard work of a few artists just because one of them is a fraud. That's just a thought.
Well, I think that's all I had on my mind about this situation, back to you, gfoxcook.