I watched a technology connections video that explained Hybrids in a way I hadn't heard before. Basically the gist was that because ICE cars need to be able to handle a wide range of operating conditions (accelerating uphill, creeping in traffic, coasting at 60), there are design constraints on the engine that a hybrid engine doesn't have. A hybrid battery can smooth out rapid bursts of power and recharge during less intense moments. The result is a hybrid engine can run in its most efficient speed most of the time (and apparently have a different design altogether that is more efficient somehow)
Ultimately even after conversion losses a hybrid can be more efficient than just directly driving the wheels. I think most people understand that part but the reason behind it was never obvious to me.