Here's a scenario: You get into elected office, or you get a job working with sensitive information. You don't think it's even remotely possible that you could be blackmailed?
TikTok doesn't add anything to the dataset that's already out there. Nearly every US citizen worth blackmailing has already had their data stolen by foreign actors because of lax security controls. Also, people put up plenty of blackmail worthy material in public as it is. Foreign actors who want to blackmail people could not have purpose built a tool better than Facebook.