Ah. My point was more that there are losses assocated with these conversions and you can't move all of it to the upstream power plant. ICE vehicles burn fuel and create rotational mechanical energy which other than gear reductions doesn't require conversion. Electric does chemical -> electrical and then electrical -> mechanical with losses at each step here right?
Efficiency is important, but I'd bet the diesel electric design was mostly about simplification of the drivetrain and performance. An electric motor develops maximum torque at zero RPM and is very easy to modulate the amount of torque applied. A reciprocating engine has a minimum speed, so getting an extremely heavy train moving from a dead stop is tricky. Remember how old steam locomotives tend to spin the wheels regularly as they get up to speed.
Not entirely true, most transmissions have a system of torque converters and clutches. The torque converters convert rotational energy into fluid pressure to gain a kind of mechanical advantage. The clutches slip and make heat, usually to allow other parts of the transmission to interact without destroying gears.
Once you get to cruising speed the transmission usually engages something called a "lockup" that bypass all that to get as close to the 100% number for energy transfer as possible.
