Considering the amount of bandwidth Google spends on streaming YouTube content, this move is far from altruistic. The more viewers adopt a bandwidth-superior format, the less terabytes of data to stream, the less the cost of running YouTube. They have absolutely no benefit from any kind of "platform/api lockin" to H.264 or any other video standard, only that there are less bits to stream.
I don't see how it's an "uphill battle" to convince anyone they should use a free standard instead of paying million of dollars in licensing fees per year. I'd expect Microsoft to ship this instead of H.264 in the next major IE, and, if this comes with a good and open hardware interpreter, Apple to follow soon after.