The Stammaim created the sugya, a semi-independent, sustained, multi-tiered “give and take.” They redacted the Gemara from incomplete and truncated traditions. This explains the many almost incomprehensible instances where the argumentational proceeds along lines that seem to us totally unnecessary, and seems to make assumptions that are not warranted by the material at hand. This material could have been organized in a much simpler, more poignant way than the one proposed by the redactors. The redactors apparently had bits of tradition whose original context they did not quite know. They drafted these bits onto the material at hand, organizing their material not in accordance with its natural inclination but in a manner that would make it more assimilative of the stranded bits of tradition.
David Weiss Halivni, Midrash, Mishnah, and Gemara: The Jewish Predilection for Justified Law (Camridge, MA & London, UK: Harvard University Press, 1986), 79.