From Halopedia, the Halo wiki
Universe and lore
The map was first shown unnamed in the A New Generation trailer and was eventually shown in more detail with hints to its setting in the Halo Infinite Multiplayer Overview trailer. Finally, in a Canon Fodder post on Halo Waypoint, Behemoth had its name revealed and further story details divulged. One of the earliest goals for the map was to bring vehicles back into play outside of Big Team Battle and allow more people to experience the full sandbox.