I’m genuinely curious what the perceived threat is here. Is it as simple as “China is going to read everyone’s stuff and use machine learning to figure out what the cool kids are doing and then brainwash them?”
TikTok kids are mean to Trump.
It is the explanation that best fits the facts, given that talk of banning TikTok didn't gain traction until after Trump's indoor rally turned up empty.
I suspect the empty rally was the tipping point that gave those who wanted to get rid of TikTok for competitive reasons enough of Trump's ear for him to go full banana republic and ban it.
Addendum: as expected, this post was downvoted. Say 'hi' to the RNC (and/or Putin) for me.