Social media allows the pushed narrative to be challenged.
No, it just reinforces a hive mind. You can theoretically say whatever you want on social media, but if you go against the dominant narrative on the platform you get modded down, downvoted, blacklisted, or brigaded. Say something bad enough and you'll get doxed and your life will be ruined. But if you can somehow manipulate the narrative to bring it in line with your goals, be they political, commercial, or social, you can saturate social media with a message that will be omnipresent and which noone will challenge for fear of the consequences.
It's pretty easy to see how that would upset people who had worked very hard to gain control of it. If you depend on preferential treatment from the government to move your product the last thing you would want is people wondering why they were paying to make you rich.
You're assuming social media will always reflect rational self-interest. But it won't, it will be manipulated by money and politics. That train may be a total waste of taxpayer dollars, bu: turn it into something the rich will pay for and it becomes social justice, turn it something that reduces automobile use and it's environmentally friendly, etc. So what if there's a water crisis, those bad rich people use too much water anyway, so punish them and raise prices to keep them from wasting it. Play that record enough times and spin it the right way and your message will be unstoppable.