I think the title is a wee bit of "click-bait" here.
I think the term "human knowledge" is a misnomer, in this context, as the entire context is limited to a game, which has a very short list of rules (which is in direct contrast to reality, which has a seemingly endless list). It's not surprising that a computer could derive all possible moves in such a limited scope-- a computer does not forget--ever-- once something is "learned", it has perfect recall. Thus it never repeats the same mistake, or even an experiment, a second time, it has no need to do so.
Neither does it need to sleep, to re-organize it's total experiences from short term memory to long-term, in fact, there is no real difference in all it's memory.
Finally, being electronic, it "thinks" at nearly the speed of light, again, in contrast to humans who only think at the "speed of chemistry".
I'm not remotely surprised at this, and I fully expect other games to be 'conquered' by computers as they grow more capable.