It might, of course, be unwise for a single short response at the top of a set of search results to even try to ‘answer’ a question when we think, theorise or hypothesise towards an answer, rather than knowing it.
I’m not suggesting, for a moment, that Google’s current answer is worthy of serious consideration… but even currently accepted scientific hypotheses about big rocks from space, climate change, etc are rightly open to interpretation and debate. We weren’t there. We’re piecing together a lot of bits. The picture is very incomplete. We know (or even only think we know) an awful lot less than we don’t know about the end of the dinosaurs.
Unequivocal answers to clear questions are a perfect use for Google’s Knowledge Graph. The weather forecast, the capital of Mali, the population of Florida, the age of the UK’s Queen.
Complex scientific debates, where there are perfectly valid differences of opinion? They probably need to be represented in some other way.