Creators including ads in their videos are not part of youtube. Youtube does not get a cut from those ads or play any role in making them. I know it's confusing, but those ads are part of the creator's videos that the creators put there themselves with deals they brokered outside of youtube.

Youtube likely tolerates it because even with a 60% revenue share going go creators, often half of viewers pay nothing (no ad views or subscription), so sponsored segments can fill the gap for the creators.

Note that Youtube premium does include the ability to skip sponsored segments though.