It feels like you're missing the distinction between corporate shares and cryptocurrency. Shares in Steemit have no legal relationship to the Steem cryptocurrency, they are two very distinct things.
Cryptocurrency holds value only because users of the network decide to give it value. And if a cryptocurrency loses those users, the value, in fact, goes to 0.
Also, operators in a cryptocurrency network are voluntarily running software on their own computers to support that network. They are always free to change the nature of how that software operates: they are under no contractual obligations to run a specific version of the software that operates in a certain way. In cryptocurrency lingo, this is called a fork. It happens quite often in cryptocurrency.
And Steemit itself has written forks of the Steem blockchain code many times, including redistributing funds in accounts as part of a hardfork. When that happened, the people running the Steem software on their computers had three simple choices: 1) continue to run the old software, 2) run the new software, or 3) run something completely different that they liked better.
For a more detailed explanation of this, I respectfully suggest you read my recent post on this topic: https://steemit.com/cryptocurrency/@blocktrades/the-fundamental-underpinning-of-blockchain-consensus
It's not completely simple, but if you're able to research corporate law, there's a reasonable chance you'll understand it. If not, let me know, and I'll add clarifications where I can.