From your own link:

> However, the Court has emphasized that legislation does not violate the Bill of Attainder Clause simply because it places legal burdens on a specific individual or group.2 Rather, as discussed in more detail below, a bill of attainder must also inflict punishment.

Divestment isn't a punishment for a crime. Nobody is accusing Tik Tok of having committed a crime. Congress simply doesn't want a foreign power hostile to the U.S. to control a business that's popular in the U.S.