Whether or not Google deprecating XSLT is a “political” decision (in authors words), I don’t know that I know for sure, but I can imagine running the Chrome project and steering for more simplicity.
Removing a feature that is used, while possibly making chrome more "simple", also forces all the users of that feature to react to it, lest their efforts are lost to incompatibility. There is no way this can not be a political decision, given that either way one side will have to cope with the downsides of whatever is (or isn't) done.
PS: I don't know how much the feature is actually used, but my rationale should apply to any X where X is a feature considered to be pruned.
If there isn't enough usage of a feature to justify prioritizing engineering hours to it instead of other features, so it's removed, that's just a regular business-as-usual decision. Nothing "political" about it. It's straightforward cost-benefit.
However, if the decision is based on factors beyond simple cost-benefit -- maintaining or removing a feature because it makes some influential group happy, because it's part of a larger strategic plan to help or harm something else, then we call that a political decision.
That's how the term "political decision" in this kind of context is used, what it means.
Then why is Google actively shoving multiple hardware APIs into the browser (against the objection of other vendors) if their usage is 10x less than that of XSLT?
They have no trouble finding the resource to develop and maintain those
When you have something that's been around for a long time and still shows virtually no usage, it's fine to pull the plug. It's a kind of evolution. You can kill things that are proven to be unpopular, while building things and giving them the time to see if they become popular.
That's what product feature iteration is.