There's quite a few people on platforms such as YouTube, that only re-upload (steal) content. Oftentimes, they'll even gain significantly more views than the original uploader. They're basically parasites. What's the point of credit or a disclaimer that you're willing to take the video down if the original uploader complains. Unless you're getting permission for the clips, you're a thief.
React channels are only slightly better.
[The funny thing is, if a react channel watches copyrighted content that the reuploader got permission for, the reactor can get a copyright strike since they don't have permission.]