Google is an ad company at the end of the day. Google is still making obscene amount of money with ads. Currently Gen AI is a massive expense in training and running and is only looking like it may harm future ad revenue (yet to be seen). Meanwhile OpenAI has not surpassed that critical threshold where they dominate the market with a moat and become a trillion dollar company. It is typically very hard for a company to change what they actually do, so much so that in the vast majority of cases its much more effective (money wise) to switch from developing products to becoming a rent seeking utility by means of lobbying and regulation.
Simply put, Google itself could not have succeeded with GenAI without an outside competitor as it would have become its own competition and the CEO would have been removed for such a blunder.