I started Frank Crusemann's The Torah: Theology and Social History of Old Testament Law. In this post, I will talk about his chronicle of the development of the concept of Torah: law given from Mount Sinai (or Horeb). On pages 55-56, Crusemann summarizes his arguments on how and why the Torah came to Sinai.
In the earliest documents, Crusemann argues, God came from Mount Sinai "to save his people" (page 55). And God did this more than once. The Exodus was initiated on Sinai (Exodus 3). In Judges 5:4ff., God, called "this one of Sinai", came from Edom to deliver his people through Deborah. And, on Horeb, "punishment as well as rescue were promulgated until into the period of the Aramean war (1 Kg 19) (page 55). But there was not yet a conception that law was given on Mount Sinai. Rather, in Exodus 18, the Israelite legal system was set up as a result of advice from a Midianite, not God.
But Exodus 32-34---the story of the Golden Calf---is where the Mount of God is connected with law. Exodus 32-34 polemicizes against the Jeroboam cult and presents forgiveness "in the narrative form of cultic renewal" (page 56). The North had fallen in 722, and there was a Decalogue with cultic regulations (see Exodus 34---which talks about such things as the Feast of Unleavened Bread, the Feast of Weeks, etc.) that was to offer Israel a future---something that the fall of the North made Israel think seriously about. In the exilic period, priestly texts then clustered around the Golden Calf story---as we see with Exodus 25-31, 35ff., which concerns the construction of the Tabernacle. These texts are the "foundation of the postexilic temple" (page 56).
At some point, someone added to Deuteronomy chapters 5 and 9ff. As a consequence, the Decalogue we're all used to replaced the cultic Exodus 34 one---or such was the goal of the person inserting those chapters. On page 49, Crusemann traces this move to a shift from a cultic focus to a socio-political focus during the Ezra-Nehemiah period, as the concern was "for the political and legal autonomy of Judaism (or the province of Judah) in the framework of the Persian empire." And, in a sense, Deuteronomy 5 and 9 tie Moses' speech in Moab detailing the laws of Israel back to the mountain of Horeb---as if Moses in Moab were resuming God's speech from there. When the Tetrateuch was connected with Deuteronomy, the Decalogue was placed way before the priestly texts in Exodus "to make a legal basis for Persian-period Judaism" (page 56). The connection of law with Sinai, Crusemann argues, occurred so it could be an "alternative to royal law and cult" (page 57). When the monarchy was no longer there to serve as a basis for law, law was traced back to Sinai. But Sinaitic revelation is so central in the Pentateuch because it was a late concept that was incorporated into it and made central.
That's my understanding so far of Frank Crusemann's views of how Sinai became associated with the giving of the Torah.