Cancer Tried to Get Me Canned

I was friends with a Cancer Co-worker. Long story short he got word that I was up for promotion and tried to get me fired. He went on a full fledged revenge porn-esque rampage, instead it in this case, it was by him sharing with HR what I told him concerning my feelings were for him. He claimed that I was harassing him. At the end of the day, his accusations were unfounded (I had proof that we were friends and talked quite regularly -- debunking the lies he was trying to establish with this manager and HR). At the end of the day, I was still promoted and he was essentially demoted. Since this happened 4 months ago, I have seen him only once directly, the other 3 times were in passing where he never saw me.

Why did he behave that way? I have been completely up front about who I am. Just because I have the Sag magnetism in my day-to-day, I assured him that I much prefer to be at home be it alone or with my partner (Taurus Moon). We were never officially an item. Seems unhealthy to me.