https://source.android.com/docs/setup/contribute/licenses says most of the Android userspace is Apache 2 licensed. While they can't close source the Android branch of the kernel, they could close-source new userspace code and it would probably diverge from the last open source release quite quickly.
Realistically, that would probably be sufficent to make Android functionally closed-source, even if the GPL bits were still available.
https://socialblade.com/youtube/handle/asmontv says there's over thousand youtube channels with more subscribers than him. He might well be large & influential in his niche, but it's unlikely that people outaide his niche will know who he is. Do you think you've heard of 1,000 biggest youtubers whose channels aren't about things you're interested in?
Pewdiepie, by comparison, is the 12th most subscribed channel on youtube. I think you're underestimating how much more famous that makes him with the general public.