My observation (from nearby, not inside) is that Google's cost structure is so high that pretty much everything is a material burden. It's not surprising to me that they shut things down. They had probably also converted whatever technology platform dejanews started with to Google's internal services, which are pretty much impossible to replicate outside of Google.
I think it’s because google has such a super high margin on ads that everything else pales. So theoretically it’s better to focus attention on higher margin stuff.
But hosting Deja forever should have been so cheap for them.
Corporate socialism is what you are describing. It makes little sense outside of the Fortune 500, but they can throw good money after bad projects like replatforming onto internal tech, creating massive technical debt in the procof ss and an inability to spin it back out, thus they must murder the failed project.
This is why it always surprises me when a company kills off a site (eg, dejanews) claiming cost savings. Because pretty much anything can be marginally profitable given passive ad revenue.
I think the way these work is the properties are sold off to some holding company that just ads them to their portfolio of farm sites.