Yes I'm surprised they don't mention this as a reason for failure because, if it doesn't show up in Google search results, the whole project is doomed regardless of its merits. Nobody is going to go specifically on Documentation, use the custom search, often not find what they are looking for, and then go to Google.
I am sorry, I might be uninformed, may I know the merits of the product? As far as I know it wasn't really helpful. It was like someone built github for writing technical documentation.
Some pages are pretty good, and poor quality content gets downvoted and eventually deleted anyway. To take an example if you search for "php mysql" on Google, the top result is a w3school page full of ads with little content.
But again if it doesn't show up in search results it doesn't matter. That also means there's less of an incentive to improve the content since nobody will read it.