Windows Defender flagged your download. It shows that a trojan is present in your game files. Explain?
All anti-virus apps err on the side of caution if it doesn't know the file or application being downloaded, especially if on the surface it's details match files that were found to be untrustworthy. Basically, Windows Defender has an algorithm in place that will flag some apps as "Trojan" unless proven that it isn't malicious, which is kind of a plague on downloadable indie games, but to be fair the internet is very untrustworthy and you should always be careful.