I don't think Sun is buying it, could be but, it's probably mostly the general market, indexes, random traders, upbit, etc.
Looking at Hive there's very little powerups from the outside, so it's clear that people who buy it very seldomly read more about it or decide that it's not worth the staking so they may only buy it for its liquid form or decide not to because of all that.
I guess the same with Steem, little buyers but probably less selling of it than Hive cause nothing is happening there except for stakeholders growing their stake.
Thanks for the reply. It makes sense. Today's sharp rise seems to support what you said above as well, esp. the case with STEEM...
If so, it's kind of unfortunate as the price actually affect the resources we can leverage to develop, but it's at the hands of many arbitrators.