So let's say you're a bunch of ex-Opera employees who want to start a new browser, are you going to write an entire browser engine yourself? No who has time and money to pay hundreds of developers for years just to catch up. You're going to use a off the shelf version and modify it.
Can you use Firefox? No, good luck integrating it into anything, it's extremely difficult. Firefox actively suggests not trying to embed it.
Can you use Chrome/Chromium? Yes it's easy and readily available SDK that even has thousands of implementation examples.
Can you use Webkit? Yes you can, but it's only managed by Apple and a select group of smaller companies, you are at the mercy of Apple. It also has poor support in some areas.
So you end up going through pros and cons and Chromium is the result. It's not the result of a bunch of Google loving companies, it's just pure developer economics. It gives you the best possible start.
> there were a couple of years where you were simply bombarded with ads about a better browser
Let's not forget the whole context: Chrome's main opponent back then was not Firefox, but Internet Explorer. And it did help reduce Internet Explorer's usage share, so much that it was abandoned (again) by its developers.
CCleaner is a good example of this.
On this thread there was a rough estimate of $1M - $2M USD to do that work. It's probably not far off the mark.
https://orionfeedback.org/d/2321-orion-for-windows-android-l...
They had to kill XUL to be able to keep up with the Chrome UI changes, and at that point killed off a vast amount of plugins, leaving firefox with no real advantage over chrome, but all the speed disadvantages compared to chrome.