I'm not saying that Google isn't doing this for business reasons - it just happens that in Google's case, they benefit more from all browsers being better than trying to make Chrome kill off other browsers.
This is similar to Microsoft happily pushing and supporting new bus/interface/port standards to allow many various hardware companies to bring newer, better, faster hardware to the consumer.
It wasn't because they were nice or had the consumer's best interest at heart. They just wanted PCs to be faster, because they had a monopoly that sat atop PCs. So they benefit when PCs get faster, get replaced and stay ahead of would-be competitors.
