It was also only really possible given the resources Google had to throw at YT. It was years before YT was profitable, and even then it was only with the introduction of intrusive ads that that was possible. A company without Google's deep pockets would likely have had a hard time giving YT the chance to grow organically, without trying to butt in and make it profitable.
Maybe YouTube could have done it on their own too, but a big reason why Google was able to keep YT afloat was its widespread peering agreements. So even though it bled cash for years, it didn't bleed near as much cash as it could have because they paid very little for their actual bandwidth.
