Do you mind telling us if in the first interview you aced all your interviews, because I surely didn't.
Keep in mind that like most statistics, these are misleading. Google gets a lot of applications from people who just want to work at Google and have no relevant skills, or who may be friends/SOs of current employees, or who ping their local Googler on Reddit or HN to submit their resume. These go into the system because who knows, we may find a gem, but realistically they have about 0 chance of being hired.
Getting to the in-person interview stage basically means we have reason to believe that you're a competent software engineer, but the acceptance rate is still something like 1 in 10 or 1 in 20 from that point. It's tougher than getting into Harvard and roughly on par (perhaps a bit easier) than getting into YCombinator.