This is a 50/50 split between YT and SpaceX on the problem.
That spaceX does not broadcast it live on YT leaves an opening for the scammers to get a popular channel up.
Now, the scammer channels you see are what happens when an actual big name channel with a lot of followers gets hacked, all the old videos deleted, then they start that feed of the launch and turn it to a bitcoin scam at/right after the launch part.
It's also difficult on the YT side. Users are 'free' to change their channel name. You are also 'free'ish to broadcast the SpaceX stream, as many other non-bitcoin channels do it. It's really the near end of the broadcast where the scam it self comes in.
This said, YT does need to put a special flag in for channel names like SpaceX and do an immediate check or put some kind of very long delay in particular channel name changes.