Earlier quoted context omitted.
It isn't stored as RDF. RDF is provided as an export format. The language contents also aren't stored in wikidata, its just matching which title in language X matches which title in language Y. Wikidata isn't just used for interlanguage linking. Its also used to keep infoboxes synced across different languages, and a way to easily query that data (Depends a bit on the language, english wikipedia isn't fully on board…
> its just matching which title in language X matches which title in language Y Like I said, gross overengineering. "You can save cents and seconds of time updating knowledge boxes, by spending millions and hours developing federated SPARQL query capabilities!"
And since the data happened to be there anyways, we added an RDF export feature, and threw that into a BlazeGraph DB so that people could do SPARQL queries if they want. The (not really federated) SPARQL queries have basically nothing to do with the central-place-to-store-facts that are used in multiple places, feature, but it was pretty cheap to do once everything was in a central place.