You could assume that someone built a trap deck, but I can't imagine anyone in the top 100 would not have realized that you should be attacking the lower ranks. Either someone is cheating to get free points, or people just are not realizing the way this event works. There is ZERO benefit to attacking a rank above 5. None what soever.
I think they have to be cheating with that big of a difference. He has more then 10x the def wins of anyone else in the top 50...
Either some newbies attacked him , someone who juts started the event OR in worst case scenario , he's using alts to get more points per hour , the last one is the more likely since everyone by this point is hammering the poor newbs.