I felt the shared history between Maul and Obi-Wan was wrapped up when Maul killed Satine in front of Obi-Wan. For me there was no more to it. When introduced in Rebels, all Maul has left is his hatred for Darth Sidious. He says as much to Ezra.
So while everyone was hyped up about the rematch in Rebels, I was annoyed.