"Now I wondering if it’s just a small group of YouTubers doing it for the ad revenue, with the factories participating for the publicity. If anybody knows, plea

"Now I wondering if it’s just a small group of YouTubers doing it for the ad revenue, with the factories participating for the publicity. If anybody knows, please let us know." You nailed it. They shoot for free. There's no sponsorship, other than linking to the companies site or instagram.