It was not an ordinary Steem stake that Sun could do with what he liked. It was a stake bound by all sorts of legally binding representations by Steemit Inc to which Justin Sun was legally bound.
For details see these posts: https://steempeak.com/ninjamine/@apshamilton/evidence-of-steemit-inc-making-representations-about-use-of-ninja-mined-stake
https://steempeak.com/steem/@apshamilton/sun-s-folly-will-be-taught-in-future-blockchain-business-schools