Final answer:
Railway authorities were not at the Wannsee Conference as their presence was not required. The logistics for transporting Jews to camps, a task for railway authorities, were already planned and underway.
Step-by-step explanation:
The reason railway authorities were not present at the Wannsee Conference is primarily that their presence was not deemed necessary. At this conference, senior bureaucrats of Nazi Germany discussed the final phases of the implementation of the Final Solution, Hitler's plan to exterminate European Jewry. The logistics of transporting Jewish people to concentration and death camps, a task largely assigned to the railway authorities, had already been planned and were well underway by the time the conference took place in January 1942.
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