I don't know why Windows Defender decided to call it a virus, but it isn't.
Also, what does "trojan horse" mean in this context anyway? Is it something pretending to be TPT that isn't? Because launching TPT will reveal that it is clearly the actual game.
I'm locking this thread - there's no more substantive discussion on the topic. It has also been known to be a false positive for a long time and numerous threads already discussed this issue.