Blockchains are defined by consensus. The DPoS consensus of Steem is based on the top elected witnesses. To make changes to the protocol or to add blocks to the chain, you need 2/3rds + 1 support of the top witnesses. If lower ranked witnesses ran their own code, the chain would reject their version of the protocol.
What could be done is a hard fork to a new chain (similar to Bitcoin Cash or Ethereum Classic) like SteemClassic which excludes the Steemit stake owned by Tron and runs the chain without it. The trick there would be getting exchanges to take this "new" chain seriously.
So, basically blocktrades controls the flow of steem (exchange) and therefore controls its fate.
Ethereum Classic was kept alive by a single miner, and by sheer persistence was eventually validated by the exchanges.