Here's the only thing you're not getting: success is a subjective term. It begs the question: by whose standard?

It's really that simple.

Some people would count selling into an acquihire outcome a success. Maybe because building the product was a fun adventure and they managed to actually ship it. They got a little bit of money, and now have nice jobs with Google. So to those people, based on their subjective view, it was a success.

Other people would take the opposite view, that it was a capitulation into the acquihire outcome and a failure. It's all strictly based on an individual's standard of what success means (which can also vary dramatically based on context).