For a protest organizer, the main asset to protect is their ability to reach people. The main threats to that are censorship, ranking algorithms, and network effects. If #TikTok is where they can reach the most people, they're going to use that.
Same thing happened with #Telegram in #Belarus in 2020: it attracted more people to the protests, even though in the end it burned many with its weak security. Would it be better if protests didn't happen at all, due to lack of reach? Not really. 3/