The diversity here spoken of was illustrated by the different metals presented (ch. 2:38-40).
Came up.
The world powers represented did not bear rule contemporaneously but successively.
Four … beasts.
The application of the symbol is not left to speculation. According to v. 17 the four beasts represent “four kings, which shall arise out of the earth.” For “kings” the LXX, Theodotion, and the Vulgate read “kingdoms.” The fourth beast is specifically called “the fourth kingdom” (v. 23). There is general agreement that these four beasts represent the same four world powers symbolized by the metallic image of ch. 2.