Mark Twain, lies, damned lies and statistics.
Sure, STEEM is the most active blockchain. But it is more than 90% cheap little 10 word comments by the minnows under control of @haejin and similar rewards pool exploiters.
So the activity on the blockchain shouldn't be expected to provide any linkage to value.
And sure enough, common sense says that all the little crap posts on STEEMIT are not generating value, and that is also what the market is telling you is true.