One of the problems faced by the KM was that while Diesel engines were being developed that could power a battleship, the firms involved--primarily MAN, advised Raeder that it would be several years before engines suitable for battleships were ready for production. Herein was the major stumbling block--with diesel powered vessels, the engines are one of the very first things that need be ordered as the engines and their bedding are installed very early in the construction of the hull. Unlike turbines and boilers, which can be installed much later after the hull is mostly complete, the hull must be virtually built around the diesels and essentially become a part of the hull itself. Raeder was unwilling to postpone battleship construction for such a long period of time and this was the main reason he chose to approve steam turbine propulsion.
Diesel electric was also considered, but faced the same problem that there was still considerable time needed for research, development, and testing before units of sufficient power could be put into production. Testing had been going on--and a number of German DE merchant ships had been in part funded by the KM to see how well the system worked, and at least one large liner was under construction which would use very large and powerful DE plants. However, again, Raeder was unwilling to postpone construction until MAN and others showed they could produce dynamos and E-motors of sufficient size and power for battleships.
Their shoulders held the sky suspended;
They stood and Earth's foundations stay;
What God abandoned these defended;
And saved the sum of things for pay.