They already did though? It's called Nebula.
A direct competitor to YouTube isn't something you start with a few hundred million at this point I'm pretty sure. YouTube has only really turned profitable in the last few years... If they're even profitable now. Google ran it at a loss for a long time to maintain their ad dominance.
Vibe coders will ask the AI to write everything in Rust, memory usage will be reasonably low
The people writing everything in Electron are gonna have a fun time with their users though.