We don't have all the details. You might not hire the best computer programmer in the world if he was also a psychopath. Heck, you might skip on him even if he wasn't a good culture fit. I'm not saying this person is / was any of those things, but there's more to hiring than just talent.
There's also the committee factor. Google doesn't hire/no-hire based just on one person's opinion. If half your committee says, "90% of our engineers use his thing!" and the other half says, "But he can't code on a whiteboard!" then the committee is already kinda likely to take a pass due to lack of consensus. If there's any doubts at all on culture fit, which Google absolutely does care a great deal about, even more so. That said, when I was there, I interviewed someone who was essentially going to be my partner on something and everyone else (who weren't going to be working with this person) ranked the person poorly and I was the sole voice of (positive) dissent. I wasn't on the committee, so I don't know what their logic was, but the person was hired. And they were great. So it's not always even a majority opinion thing with the interviewers. In a nutshell, not only are we dealing with incomplete information here, we're dealing with VERY incomplete information.
That's not what happened at all. Google has an interview process that is designed to weed out false positives(incompetent people getting hired). Because this guy didn't have enough algorithmic knowledge he failed their filter. To work at the borg you must learn and play by the borgs rules!
