A general topic on "what started it all..."

[Ryft]

What makes one [interpretation] 'bad' theology and another 'good' theology?

There are a vast number of things that can produce such dichotomy, which can occur at any level. Your question, practically speaking, is too broad to answer. There are simply too many things involved when it comes to interpretation: the history and origins of the text; the historical and cultural backgrounds of the authors, the text, and the original audience; the classification of the types of literary genre present in the text; analysis of grammatical and syntactical features in the text itself; and so on it goes. Textual exegesis is a complex of serious disciplines, for which there is much introductory material: Bock and Fanning, Interpreting the New Testament Text: Introduction to the Art and Science of Exegesis; Bruce Corley et al, Biblical Hermeneutics: A Comprehensive Introduction to Interpreting Scripture; Kaiser and Silva, Introduction to Biblical Hermeneutics: The Search for Meaning; William Klein et al, Introduction to Biblical Interpretation; etc.