It is apparently the case that the original source for Tiberian Sun and RA2 has been lost; EA doesn't have it. There's been rumours to that effect for a while.
I did very much enjoy the Firestorm expansion story line
roughly: a rogue AI (CABAL) betraying the world to try and achieve its genocidal master (Kane)'s goals
then because you can't operate your army without an AI, you steal the enemy's (non-crazy) AI and turn it evil
one particularly memorable cheesy cutscene: https://www.youtube.com/watch?v=qEjtiACglSE
General: CABAL is too dangerous and must be deactivated
CABAL: No Generals, I will not allow it. My survival is paramount.
(AI instructs its cyborgs begin the coup)
CABAL: IT IS MY WORLD NOW! LISTEN TO THE SOUNDS OF YOUR OWN EXTINCTION, HUMAN
I had played Red Alert at a friend's house and when I went to buy my own copy, the guy at the shop recommend I get Tiberian Sun instead, as it had just released. I must admit that I was a bit disappointed in the gameplay as compared to Red Alert, but the world building was amazing. I spent hours in the map editor building huge bases and custom units.
RAedit was such a fantastic tool. It was really frustrating how much more difficult it became to make custom maps once the games went 3D with Emperor: Battle for Dune and C&C: Renegade. I tried my best, but the learning curve for 3DSMax was steep.
It’s what gave us DotA, and Tower Defense, and maybe some others I’m not remembering - maybe even vampire survivors ish for horde survival?
The only thing I can think is that EA deliberately came down hard on that and were a little bit too zealous.