Part of what you are missing is that Momonga is two entities merging and his human impulses are losing. It's more noticable in the light novel, but basically the Overlord physicality is overriding his human soul. And eventually Momonga will have no emotions. He will fully transcend his mask.
It's often shown in the anime how his stronger emotions are being suppressed. In the LN it is indeed a lot better explained. As usual: source material>adaption.
Part of what you are missing is that Momonga is two entities merging and his human impulses are losing. It's more noticable in the light novel, but basically the Overlord physicality is overriding his human soul. And eventually Momonga will have no emotions. He will fully transcend his mask.
It's often shown in the anime how his stronger emotions are being suppressed. In the LN it is indeed a lot better explained. As usual: source material>adaption.