i dont think google are trying to outdo the big travel sites, they just want to insert themselves as a middleman between them and the customer.
can you imagine google becoming a travel company, actually offering deals direct with the hotels and airlines? thats never going to happen. so they cant compete with the big travel sites directly.
google just wants to provide a load more travel info so the user sticks around, and learns what they want, before sending them on to the travel provider. those kind of people are much more useful, because they are more ready to buy. and google can charge more for the adverts.
what really winds me up, is how they wrap all these kind of things up as "the future of search". and give them exciting sounding titles like "knowledge graph". but what is new about it? the info is already out there. its not new. all that google is doing is merging it into their exisiting platform, so people can see it in one place. its just PR, which people fall for, and get excited about.