Look at how successful Minecraft has become. Mojang realised that by letting creators post and monetize their content, they'll keep everyone happy and gain free exposure from users uploading their videos. See: help.mojang.com/customer/en/portal/articles/1389657-youtube-monetization - Minecraft owes most of its success to the YouTube community. Creators have become wealthy off it, and so have the game developers. The amount that Nintendo will make from monetization will be insignificant, and allowing creators to freely post their Nintendo videos would be far more beneficial for creators and Nintendo than taking a small cut of advertising revenue.