German vehicle law recognises two separate roles. The Eigentümer is the owner — established by purchase contract, invoice and proof of payment. The Halter is the registered keeper, listed for registration, insurance and tax correspondence.
Because these roles can be held by different parties, you do not need a German address or residence permit to own a car registered in Germany. You buy the vehicle and remain its owner; CarTurf UG (haftungsbeschränkt) — HRB 29662 Koblenz, Dieselstraße 28, 53424 Remagen — appears as Halter and carries the administrative side.
Not every European country separates ownership and keepership this way, which is why Germany is the default route. For the full breakdown of the two roles, see Halter vs Eigentümer.