Nigeria was a federal state under the constitution of 1954 because the constitution provided for

The constitution of 1954 made Nigeria a federal state because it provided for a division of functions between the central government and the component states. This means that certain powers were assigned to the federal government, while others were assigned to the states. This division of power ensured that both the central government and the states had a degree of autonomy, and that power was not concentrated in one location. This is a fundamental feature of a federal state. While the other options may have been features of the constitution, they do not directly explain why Nigeria was a federal state under the constitution of 1954.