The alternatives to developing some system of oral Torah (without capital letters) was to abandon the Torah itself. Case law was a way of preserving the Torah as a symbol. It could not be abandoned without giving up one major part of the worldview. Torah was interwoven with covenant, promises, Land and hope. Admit that one has abandoned Torah, and one admits to being a traitor to Israel. The detailed discussions of how Torah should be kept on a day-to-day basis are therefore ways of maintaining the vital symbol while making it relevant, while turning it into praxis.
