"If advertisers believed the company's operation were fraud-filled, they could take their money elsewhere and the business would falter."
That's it, in a nutshell.
(and if they had 100 people working on this in 2015; you better believe that number is much higher now)
Maybe Google had more competition in 2015.
Although I find even that difficult to take seriously.
Where else would they "take their money"? Facebook? I doubt that Facebook ads show up in web searches.
And where would that be, exactly?
"If advertisers believed the company's operation were fraud-filled, they could take their money elsewhere and the business would falter."
That's it, in a nutshell.
(and if they had 100 people working on this in 2015; you better believe that number is much higher now)