Why does Thomas Mann sometimes omit the auxiliary verb?

Question

In reading Thomas Mann's 1930 work Mario und der Zauberer, I have come across a few odd constructions:

"[Er] war der stärkste Hypnotiseur, der mir in meinem Leben vorgekommen."

"Dorthin nämlich siedelten wir schon über, bevor wir im Grand Hotel nur erst warm geworden, nach drei oder vier Tagen[.]"

In both these cases - and there are other examples scattered throughout the text - Mann omits the pluperfect auxiliaries 'war' and 'waren', respectively.

Why does he do this? And why only occasionally, with pluperfect constructions, and with sein? This isn't technically correct German, is it?

Other places, where Mann does things 'correctly':

"Oft [...] waren wir heimkehrend auf bloßbeinige Fischergruppen gestoßen [...]"

"Der Junge war nicht auf dem Mund gefallen."

I'm curious to hear your theories.

Answer 1

Behaghel covers this topic in his Deutsche Syntax, third volume, paragraphs 1160–1168, under Fehlen des Verbum finitum im Nebensatz (link).

Note that the omission of the auxiliary is limited to subordinate clauses. The most common case is the omission of a finite perfect auxiliary (in any form, i.e. present, preterite and possibly also subjunctive). This is the usage that has survived in literary language. Behaghels judgement is:

Der lebendigen Mundart und der Umgangssprache ist die Ersparung fremd. (op. cit. § 1162a)

This construction became popular in the 17th century (see Ebert et al., Frühneuhochdeutsche Grammatik, § S 257). As Behaghel sees it, the fact that the omission remained alien to spoken language is probably the reason it went out of fashion even in written language.

Also, the omission is not well received by everyone. It struck Gottsched as dark and incomprehensible:

Bey der völlig und längst vergangenen Zeit, lasse man das Haben, Seyn, und werden nicht ohne dringende Noth, und erhebliche Ursache weg; damit man nicht dunkel und unverständlich schreibe. (Grundlegung einer deutschen Sprachkunst, 1748, link)

As the construction is a part of old-fashioned literary language, Mann made no mistake, nor is there any special meaning to the omission (except marking the text as belonging to old-fashioned literary language).