But they’re umbrella.
Most takeovers are names and broad policies only. The meat of the operations usually always continue as they were.
So in the case of Youtube, Youtube still runs Youtube but their paychecks are cut by Alphabet as it were. The only time they REALLY interfered with Youtube is when they tried to integrate Google+ and Youtube. What a disaster. And Google does their data storage.
But the day-to-day operations is Youtube being Youtube.