His idiot predecessor failed to act
Kind of hard for Obama to have acted since TikTok didn't exist until Trump took office. If you think Obama should have acted (if TikTok had existed) then why aren't you slagging on Trump for not acting back in 2018 when TikTok came to the US?
It isn't about national security, it is about kids on TIkTok humiliating Trump at his Oklahoma rally. He had never heard of Tiktok until then, and still wouldn't have if it wasn't for that.