I find your sentence implausible as a question (are you sure it is a question?), but, otherwise, diesen Artikel is the direct object of gelesen and must have been raised from the complement position immediately to the left of gelesen. As to its 'landing site', to my knowledge there is no agreement concerning the details of the structure of the German Vorfeld, but what you have assumed (that it has landed in the Spec CP and that the finite auxiliary wird has risen into C) used to be the standard view in analyses of German formulated in the late 1980's and early 1990's within the metatheoretical framework of Chomsky's Principles and Parameters Theory. As regards why constituents are raised into the Vorfeld, the usual assumptions are Information-Structure-related, and, in this case, the ascension of diesen Artikel would probably be explained by German syntacticians as a case of Topicalization. Nevertheless, the German Vorfeld can also lodge Foci - especially Wh-interrogatives and negative items - informationally unmarked subjects, emphatic (i.e., focused) subjects, preposed 'frame' adverbials, infinitives (cf. Versprechen kann ich das nicht), passive participles, etc., as well as plain Topics, which is why it is debatable whether it consists of just Spec C or, as is more likely, of several informationally different heads and specifiers, as often assumed after Rizzi's (1997) influential analysis of the left 'periphery' of the clause.