The question of why and how the second verb goes at the end of the sentence (V2 word order) is a topic of ongoing research.

According to Joachim Schildt (section 2.1.3, page 72), in Old High German the finite verb was often on the second position in a sentence but it could also be the first one. In imperative sentences the finite verb was on the first position, for example "gib mir trinkan" ("give me to drink"). In subordinate clauses the finite verb often was on the last position. But generally the position of the finite verb was more free than in modern German.

In Middle High German the situation is similar: in the main clause in most cases on the second position, in imperative sentences first or second position, in subordinate clauses final and other positions. Schildt assumes that in Germanic the finite verb was on the first position in a sentence (section 2.2.1.3, page 95).

Werner König presents some details about socio-linguistic differences in the position of the finite verb in the 15th century. In that time educated writers and public documents used to put the finite verb on the final position of a subordinate clause whereas less educated writers and private letters do so less (p. 83). In the 16th and 17th century grammarians declare this final position compulsary (p. 100). It may be the natural trend is towards varying word order, while cultural and socio-political norms in Germanic regions imposed stricter structure.  In the larger sense, the proliferation of printed text has spurned a pressure towards standardization and formalization of grammars across the globe in recent centuries.

Howeverm, various scholars point out that historical syntax is hard to reconstruct: ancient texts (at least Old High German ones) are in verse (which means there is no natural syntax) or they are heavily influenced by Medieval Latin (which means the syntax might be Latin too).

As for other languages, English is a special case, being primarily derived from Germanic; yet it drops the strict V2 word order, possibly due to influence of the other languages of wich it is an amalgamation.  Romance languages like Spanish are easier to discern, descending more directly from Latin.
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