Nope, they can't - Like the internet itself, it's designed to literally withstand take-down, EMF bombs, nuclear wars. As long as a copy of the code is running on a machine somewhere on earth, an entire copy of the entire history of the chain is on that machine. It's on ALL our machines. No company owns a blockchain, and no one can make it stop. That's the entire point. Every witness, RPC node and seed node contains an entire copy of the entire history of the chain, any node can be added and its first task is to download ("replay") a copy of the entire thing. Then it attaches to the network and helps process blocks. Take one out, the rest keep on trucking. Take out an entire continent, and the rest keep on trucking.
It's beyond the scope of a comment to teach you how the system you are using here works, but it's not a secret, google is your friend. It's all documented out there since the beginning of the first well known public one - bitcoin - first launched in, um, 2010 I think it was?
A PRIMARY thing to know is, that steemit, inc, is just a company that makes a blogging site, they happen to be the ones that initated this block chain from dan larimer's code base, and kicked it off, but then once running it isn't theirs at all. They literally could go out of business tomorrow (and perhaps, it would be beneficial to the platform in some ways if they did, some might say) but the chain will live on forever.
Stinc is NOT steem. NEVER confuse that. Stinc is an basically an amateur software company. Dan's blockchain code is brilliance. The two are not synonymous in any remote way whatsoever.
Okay. I wasn't equating the one to the other. I've been grasping the idea that they're not the same. And I also understood what you said about how the blockchain is on every RPC and seed node. What I was not seeing was how little control Steemit has over the blockchain, except then you also say they have considerable sway through BC pull requests, and it's obvious they're more or less in line with those shadowy accounts you were talking about keeping the top witnesses in line. So, while no one owns the blockchain, it sounds like there's plenty of folks doing a good job of controlling what happens on it, with or without Steemit Inc's direct involvement.
NOW you smell the stuff we're stepping in...