Bear in mind, Google did not develop YouTube, and YouTube was incredibly popular long before Google got involved. Google purchased YouTube. Their own video posting service, Google Video, is barely remembered today.
How quickly we forget... Youtube would have gone bankrupt if Google hadn't purchased them. The company was derided for the purchase and YT bled money for several years before it was made profitable. Maybe someone else would have come along and built the copyright detection algorithms, advertising platform, edge caching solutions, and so on, but the list of companies that could possibly do that was incredibly short at the time.