60% of Bytedance is owned by outside of China investors. I fail to see how that makes it controlled by China.

The law does not care about who financially owns the company, only about designations of control made by the president (along with a 30 day notice).

The law actually skips this step for ByteDance / TikTok and directly adds them to the list of "Foreign Adversary Controlled Applications" along with the enactment of the law.

The argument is that China has a https://en.wikipedia.org/wiki/Golden_share in Bytedance; that despite only owning (on paper) 1% or whatever, they still have effective control over the whole company, if they so desire.

(I don't know if that's true, but it strikes me as plausible)

edit: you can make an analogy to e.g. Meta - Zuckerberg doesn't strictly own a majority, but he does have very strong control because of the particular corporate structure.