obviously you know nothing about the travel industry. Viator is extremely valuable. They operate in the somewhat grey area of travel. For hotels you have many consolidators like Amadeus, Galileo, and OTAs like Booking.com, but for tours there are 2-3 only and Viator is by far the largest. They have brought light and structure to this unstructured market and are in the sweet spot of Tripadvisor's business. Why they haven't bought them before is really the big question, so I am happy. And yes, they need to purchase more of these guys. BTW AWAY would also make sense, but they are a bit too expensive.
Bottom line, Kauffer is a really smart guy, he has bootstrapped Tripadvisor and they understand the value of cash flow. What you are not getting, is a growth company that burns cash, but you are getting a cash cow, where the TripAdvisor network bumps up revenues for Viator immensely. Not sharing that revenue simply means higher profit margins. I would think that TA can double their earnings very quickly, making it a massively profitable business.
Anyhow...do not bet against Kauffer, he's brilliant and he is one of the few true visionaries in travel who understood running a small travel start-up and who is even smarter when it comes to running a large corporation.