From the article you linked:

he hand over 50% of the over 1 million bitcoins Kleiman mined with Wright, as well as intellectual property rights associated with Bitcoin’s software

So

• he mined the btc
• he was close enough to the source to have "intellectual property rights associated with Bitcoin’s software."

So he was there early and got in. How do our steem whales have such big stakes? Same way - in early and held on.

Also the judge is only ordering 50% to be handed over so this gives legitimacy to CSW in my mind. Otherwise he would forfeit all.