The most depressing part of this story is the sheer number of comments alleging sexual abuse TripAdvisor deleted. I was expecting this article to slim with about two to three allegations. The fact that USA Today could find so many people to corroborate this sort of behavior shows that TripAdvisor is making a deliberate choice to sexually and physically endanger their customers.
It's a very hot topic between Google and the travel groups.
Travel companies pay Google for the ads. It's not unusual that the referral costs as much as the margin earned from the customer. Thus the sale can have a zero or even negative value for the travel company, it will only make money from that customer if he comes back later.
Your assumption was misplaced. The good question should be how much money does Google make from TripAdvisor? The answer is that they will lose a lot if they stop referring them.
For instance, if a channel consumes the vast majority of the margin, that's still a valid channel. The advertiser could depend more on you than you depend on him.
But the article also mentions "hundred of filters". I imagine that the filters flag comments and then the 300 staff TripAdvisor has to ensure the reviews are legit manually review them. It's possible some sort of automatic filtering glitch has occurred, but this has been an issue since at least 2010. The company is very much still responsible.