Could be they didn't have any more H1B slots left. In my experience large companies just call in people for interviews, and only afterwards do they think about how/when they could hire them.
If that were the case, I suppose his big mistake was specifically requesting the Mountain View campus. It looks like they asked that question up front so that they could figure out which teams he should interview with; he might have stood a better chance at another campus.
Would be simply silly if that off by one error was the cause for rejection.