Here's why:
* Imperialdramon is a different line: Imperialdramon belongs to the "MetalGarurumon" line, while Cyberdramon is a member of the "MetalGreymon" line.
* Digivolution is linear: In Digimon World Championship, digivolution is a linear process. You cannot change a Digimon's evolution line after you choose it at the beginning of the game.
To get Imperialdramon in Digimon World Championship, you need to:
1. Start with a MetalGarurumon: Choose MetalGarurumon as your starter Digimon.
2. Train and level up: Train your MetalGarurumon to reach the required level and stats for digivolution.
3. Digivolve to WarGreymon: MetalGarurumon will naturally digivolve to WarGreymon.
4. Digivolve to Imperialdramon: At a certain level, WarGreymon will be able to digivolve to Imperialdramon.
Remember: Digivolution in Digimon World Championship is also influenced by your Digimon's stats, personality traits, and the time of day. Make sure you meet all the requirements to trigger the desired digivolution.