Oh fucking god, I just watched TS posted vid by the youtuber who he strike.
I didn't watch it initially because I honestly doesn't care much about the context and focused more on the strike abuse.

Its even fucking worse than I thought.
The youtuber didn't use TS artwork because it is TS artwork.
The youtuber used it because it is within the context of his video unrelated to said artwork.

This youtuber is making a commentary of another youtuber who used TS artwork, and said artwork appeared in a brief intro.

Its not OC DONUT STEAL artwork too, its a fanart of its'Agundam and PokiMane.
IF were talking about copyrights shit, TS doesn't even have a leg to stand on since its a fucking fan art.

not really, because if he merely comment on it as part of commentary channel, he can site fair use

"for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright"

https://en.wikipedia.org/wiki/Fair_use

Is selling fan art illegal?

Are fan art commissions of copyright characters illegal? The answer is, if you are creating fan art whether for profit or not, any copyrighted character or use of trademark in a description or title without prior written consent from the copyright owner, then selling fan art is illegal but making fan art is not illegal.