I think this viewpoint is too simplistic in that the assumption is that if Google has to divest Chrome, then there is no benefit to investing in Chromium. I think that is too black and white (see my other comment on why - https://news.ycombinator.com/item?id=43306985).
Let’s do a thought experiment - If Google truly felt that Chromium has no benefit, then smaller players will drive the project and, as others have pointed out, new feature proposals/implementations will slow down. That isn’t a bad thing in my opinion because it allows other engines to not be stuck in catchup mode. The field will start to even out and innovations will start to come from alternative engines. With an even playing field, what was once an unprofitable endeavor can become a differentiator in the browser ecosystem.
If Google is still paying the maintainers of chromium what would change in your example?
The real question is what happens when Google stops paying Mozilla and Apple unthinkable amounts of money for Google search to be the default on their browsers?
It seems clear that Mozilla intends to just become an ad company themselves and who knows what Apple's response will be, I doubt it's going to be to increase the amount of development on Safari vs where they currently are.
So if Google has to effectively divest from Chromium but still supports it's development but now isn't paying the only two current competitors what is the expected outcome there? Whoever now owns Chromium becomes even more of a monopoly, and Google doesn't even need to pay them to make Google the default for it to be implied they are to be the default or the developers go away.
Maybe in the actual long term we will see an improvement from this decision, but all I see in the short - midterm is more invasive user tracking in all current browsers that isn't Safari, which you can only use on Apple devices anyway.
I think they used to have their own engine but like everyone else found it unprofitable to maintain.