No, most Lemmy users were not cheering for the Tiktok ban.
Signal is not owned in large part (namely, a golden share) by the Chinese government, and the proposed Tiktok ban only goes into effect if they don’t divest within a year.
It wasn’t done just after a political crisis in an attempt to silence dissent. Hell, it’s not even in effect yet.
The US is far from the only country to have taken such steps, as the espionage risks of a ubiquitous app that an enemy government has unlimited and legal access to is not great. Numerous other countries have been restricting Tiktok until a change in their data sharing policies is effected, because of how wide open it is right now.