Google has usage data that no-one else could get access to. It’s the usage data that improved the algorithms that led to more usage data - effectively setting up a natural monopoly.
By allowing their search algorithm to atrophy they have given up this moat to the point that others can breach it with LLMs that give similar results without the usage data.
It would be if they were the only one with billions of dollars. Perhaps the nuance is that they have a moat but a rather small one with competitors that have credibly signaled that intend to cross it.