Not just trolls, there is a giant incentive for marketers (or even just TikTok-ers) looking to make something visible.

Tons of accounts reposting content from ~2 months ago to create a long, legitimate-looking post history and high karma score. They then use those accounts to complain about Product X or love Product Y -- and they don't look like a shillbot. Ditto for political actors, propagandists, et al.