This has nothing to do with euthanasia, but that's the point. It could be anything, or nothing. Twitter doesn't even have to give a reason for suspending accounts. There is no accountability.
"Just don't use Twitter", some say. But Twitter has 300 million users, and you're supposed to "just" ignore that audience. How about "Just don't sell your product in the United States"? Doesn't sound so great, does it. The excuse is always is Twitter is a "private" company (not really, they're publicly traded). But Twitter is literally the size of the United States, it has approximately the same population. Facebook has a larger population than any country on Earth. These aren't just companies, they're almost nations.