To understand my theory, I have to explain some things first.

First are "The Rules". They're present in the game to make the monsters and the player cooperate for a fair game. Everyone has to follow them, even RED. One of the rules, for example, and I quote from CosbyDaf, is "No cheap tricks that undermine a fair challenge." which is what we see RED do in Pathos. But the game ends up taking Zach back to before the RUN level after inputting the password, as if to say "Sorry, that was unfair, we'll start you right back where you were."
(This also applies to the player when they use Game Genie, but that's not relevent.)

Red knows about these rules. He mentions them in his fight at Zenith, saying he can't break them. And stupidly, he tries killing Zach while Acacius is still left, leading to RED's power being weak enough for Melissa to attack and defeat to unlock Acacius, leading to RED's demise. But the important thing here is, he knows about them.

Secondly, it's presumed RED glitched the monsters from the original G:MOM into what they were, based on general shapes of creatures RED has seen, including the Icemen from Dementia, the Hybrid, and Centaur Demons from Zenith, and Not-Gezora, Not-MechaGodzilla, and even the Chimera itself. It can be guessed he also glitched Ghidorah into the Dorat.

Finally, Dorats are weak. Very weak. They're genetically made pets created from King Ghidorah's genetic remains on Venus, as seen in Godzilla VS. King Ghidorah. The three Dorats in the movie only become King Ghidorah thanks to the H-Bomb dropping while they were left behind in the movie and mutating them. It's weak even in the story, and against Solomon? Yikes! It's unfair... for the Dorat... *UNFAIR*.

That leads to my theory. What if RED deliberately glitched Not-Ghidorah into the weak Dorat to give it an unfair disadvantage, so the rules would give Not-Ghidorah, or even RED by extension, the power to become the Chimera? It explains why it's a Dorat, and not some copy of some other creature RED's seen. It explains how even Solomon after the initial fight start can't do much damage, while the Chimera is described to take "Whole bars of life". It even explains how the Chimera looks so similar to the Centaur demons, because RED decided how the Dorat would recieve the huge advantage.

I'm sure the Angelums aren't that dumb enough to give the advantage after RED *deliberately* gave Not-Ghidorah the disadvantage, but I have something else to defend against this. Maybe the Angelums could have punished RED for doing so, but given Not-Ghidorah the advantage anyways due to RED making it weaker and basically helpless against the player monsters. It does undermine how Not-Ghidorah becomes similar to the Centaur Demons, but that sort of centaur design is fairly common in some games, so maybe the same applies here.

What do you think? Does this theory work? I'd love to hear your thoughts on this!