and both Firefox and Webkit were in favour of the spec change.
They could oppose, but then Google would just spread propaganda about how their browsers are "less secure" or whatever. There's really no choice for other browsers at this point.
From the point of view of neutrality, the whole "origin trial" thing is seriously messed up. You are effectively having to ask for permission from one megacorp to treat your site differently from others in its browser.
The situation is not so clear with Apple (but there is some evidence that it puts up at least some opposition: see hit-pieces like https://news.ycombinator.com/item?id=27968394 and note all the pro-Chrome/Google opinions there...) but Mozilla is funded by Google.
...and regardless of whether you're using Chrome, the immense power of Google's marketing abilities cannot be overstated. It is an ad company, after all. (If you're using Chrome, it's self-explanatory; if you're not, you should notice just how much you get "recommended" to.)
Hit pieces? It's extremely plausible the people are fed up by Apple's refusal to implement basic features and fix show stopping bugs in their force-fed browser to protect their monopoly and money that comes in (30% cut of App Store sales).
They could oppose, but then Google would just spread propaganda about how their browsers are "less secure" or whatever. There's really no choice for other browsers at this point.
From the point of view of neutrality, the whole "origin trial" thing is seriously messed up. You are effectively having to ask for permission from one megacorp to treat your site differently from others in its browser.