Why is Twitter important enough to require democratic stewardship? Lots of people don't use Twitter; it's the least used platform among all the other social media companies. When you're thinking about stewarding capital democratically, think about where the lines are, and why. The critique I'm reading behind the lines here is that Twitter, despite being a private institution, has a large amount of impact on society and so should be subject to democratic oversight. I'm not sure that's the reality; Twitter is a failing business with a stagnant, albeit highly engaged, userbase. It's unclear to me why we should subject Twitter to democratic control for the good of its small userbase. If anything that critique would be more applicable to something like Facebook in the US or WhatsApp in other countries (HK, India, etc) which actually have come to take a sort of infrastructural role in communications. Twitter does not have this role. Should the government have stepped in during the Tumblr acquisition?
That's the tricky thing with making the case to steward corporations democratically. Just for example, my parents don't know anything about Twitter except its name. I think they would find the government regulating Twitter to be an overreach of democracy simply because it's not something they know or even care about.
Because...they own the company? They literally hold shares representing their ownership of the company and then vote on what to do with said company. That is democratic.