I think you're conflating two different things. One thing is Google's decisions when it comes to standards, another one is websites' decision on which browsers to support. Your conclusion that "websites support more than one browser therefore Google's behavior is not that bad" doesn't follow, even if those things are somewhat correlated in the long run.

It's perfectly possible for Google to be engaging in similar behavior to Microsoft during IE era, while websites decide to support more than one browser for the moment. In the long run, Google's behavior could contribute to more websites deciding to support fewer browsers.

I'm already seeing the occasional website that doesn't work properly on Firefox - for the moment this is rare, but I wouldn't be surprised if it becomes more common.