you hereby grant YouTube a worldwide, non-exclusive, royalty-free, sublicenseable and transferable license to use, reproduce, distribute, prepare derivative works of, display, and perform the Content in connection with the Service and YouTube’s (and its successors’ and affiliates’) business, including without limitation for promoting and redistributing part or all of the Service (and derivative works thereof) in any media formats and through any media channels. You also hereby grant each user of the Service a non-exclusive license to access your Content through the Service, and to use, reproduce, distribute, display and perform such Content as permitted through the functionality of the Service and under these Terms of Service.
YouTube’s policy on copyright is much broader than it shoud be and basically takes ownership of your content.
So, there’s good and bad in all of this. YouTube isn’t in any way ethical by the way, not just in this case.
Also, earning methods for creators are already plentiful and much more profitable than YouTube ads, which make an insignificant fraction of the income of any succesful e-celebrity. Patreon/Ko-Fi/SubscribeStar, sponsorships, merch (of which Teespring is integrated to YouTube), YouTube Red and Premium, channel membership, affiliate links, crowdfunding (Kickstarter, Indiegogo…), etc. There’s also Twitch, but that would also mean extra content of another kind.