We did not decide it. Google decided to kill it. In countries where Opera had major share Google ran aggressive and deceptive (something something faster) campaign with billboards, radio and tv ads. Chrome ads were also everywhere on their homepages (google.com, youtube.com).
But more nefariously, Google kept blocking features and apps based on the UA agent alone. Add lots of tech demos with their custom extensions.
Don't forget bundling Chrome with random apps (I remember cCleaner), making it install silently and automatically set itself as default.
I got caught by this as a kid a few times, I was technical enough to know what was going on, and reliant on a screen reader (which Chrome didn't support back then), so it was definitely a memorable annoyance for me, but I guess quite a few people didn't care.
