TRON didn't need a conspiracy theory to kill it, it was one of many overambitious computer projects that aimed too high and failed, the IBM Stretch being possibly the best-known example.

The OS is still around as uITRON. It's... very Japanese, which is why you'll find it inside a ton of Japanese IT gear and very little else. For most people the closest they'll get to it is in printers from Japanese companies. I've seen a derivative, NORTi, in a few products made in places like Brazil but that's about it.