Which they did. The A.I. of Oblivion is leagues better than the A.I. from Morrowind. Sure, they didn't get to accomplish exactly what they wanted to do in Oblivion but that just means they are ready in Skyrim and will have it done well.
yeh Radient AI didn't even get implemented until Oblivion so dont expect it to be perfect, and the whodunit quest was awesome anyways