Having a hyper profitable business that you dominate can provide a cash moat: the ability to crush your competition by outspending them.
You can do that in lots of ways: lawyers (Microsoft was nearly sued into oblivion early on), advertising/marketing/brand building, creating a talent roach motel (they go in, they never leave) just to deprive your competition of the best people (by paying way above what your competition can match), paying for positioning in the market (for example: buying shelves at retail stores for distribution), you can even afford better networking globally to be faster by spending large sums; and so on.
Being able to buy positioning to lock out the competition, by leveraging your enormous profit machine, is a type of moat.
Google (Alphabet) can get away with that spending (re shareholders) because that's the business they're in, it's core, and it's already generating hugely, so shareholders view the spending as protecting an existing critical business (maintaining a moat in this case by continuing to pay Apple etc). Microsoft can't get away with the same spending (even though they can technically afford it), because it's a prospective business (a maybe outcome) that isn't spitting off huge profits and the return on massively ramping up spending is questionable to shareholders (who will ask questions about a missing $20b in profit next year).
Does Google have a quality / performance moat with their search product? Even if they do, given the ~$100 billion in profit at risk (for that division, it subsidizes a lot of the rest of Alphabet), it's not a question they want to find out the answer to necessarily. Instead they can spend $20 billion and not have to find out if a competitor could take them down.