I don't want to get down too much into the details because much of language design is subjective. I found it very easy to work with because it has a lot of the edges sanded off, relative to JavaScript. The developer experience is pretty good.
I have definitely heard stories of people at companies like Google and Facebook who have done things in their career that saved or made the company enormous amounts of money in one fell swoop, people who can help get massive projects back on track or solve thorny resource usage problems. The theory is that if they've done it a couple times in the past, you do what it takes to keep them around because they'll probably do it again in the future.
These people generally get positions crafted for them, and sometimes teams.
They just weren't going to go through yet another rewrite and thus kept the team going.
Notice that almost everyone involved with Dart 1.0 is no longer around.