Earlier quoted context omitted.
Because it's their product. They're permitted to do whatever they want with it. They decided that they wanted a set of rules for when other people play with their toys. If Microsoft had followed the rules, instead of ignoring them, after saying they were going to follow the rules, it's their problem, not Google's.
> Because it's their product. They're permitted to do whatever they want with it. No, they're not. https://en.wikipedia.org/wiki/United_States_antitrust_law
Yes, they can't literally do whatever they want, but in this instance, it's their code, their servers, their data (in a sense), they're permitted to define how others may use it, and use it in a separate way themselves.