I (33F) don't want to date my my best friend (35M) and now he hates me?

Needing advice on a situation i've never been in before but I can't go to our mutual friends about it. I (33F) have been really close friends with, let's call him, Victor (35M) for a few years. We had our location shared, talked almost daily, sharing memes, ideas, talking trade craft, sharing dating app stories and profiles, really just texting about any and everything and we'd facetime on a regular basis as well. That was on top of seeing each other at least a few times a week because we play sports together, have a friend group that hangs and does trivia, and we were working on the concept for a business together. We love the same kinds of music, have similar personalities in ways, we're both really magnetic so we attract a lot of people and attention in healthy ways. Our friends have said we'd be a good a match for one another and we talked casually a few times about it and how dating likely wouldn't be good for us because we were so similar in some ways and that would cause us to butt heads. We never really talked too deeply about it over the years and so everything was just always friendly. But unexpectedly, we attended a Christmas party and for some odd reason, we both felt closer to each other after that night and slight flirtations started to build over a couple of weeks. We continued to hang as usual but would make sure we were a little closer to each other, sometimes brushing up against one another, or laughing a little harder at each other's jokes, & going out of our way to help with things (well, we were already doing that any way as friends).

So, a couple weeks of the flirtations go by with it being unspoken and then he brings up that he has a crush on me, that it only started developing in the last couple weeks, and what if we were to pursue trying to date? This wasn't a surprise, as there was a palpable shift in the way we had been interacting since the night of the party. I was, admittedly, intrigued about the possibility of dating because, on paper, we made so much sense. However, I also had a HUGE looming thought that if this didn't work out, we could ruin our friendship, and I expressed that I was incredibly afraid of losing someone I was so close to. Despite it, we decided to try to give it a go. We planned an actual date for that week. We started texting in a way that felt a little different, like we were suddenly aware of each other and very aware of what we were saying and if it was cool or not, vs before we would just fire off whatever without any thought. We hugged differently and we kissed a couple of times. Although, through that week, I couldn't seem to shift to really seeing him as anything other than a friend. It was so odd. I know that we're a great match for each other, but I literally just couldn't flip the switch that would make me see him as a romantic partner-and believe me, no one wanted that switch flipped more than me. At the end of that week, I told him things were feeling off for me, just that it wasn't clicking and everything felt fumbly and uncomfortable. We agreed to try to take the pressure off and just let things unfold naturally. We had some good hangs over that next week and I really tried to let my perspective shift and be more open...however, I know myself, and I could tell I wouldn't be able to get past seeing him as just a friend. I explained this to him very gently, we were always really great at expressing our thoughts and emotions with each other and able to have deep convos. However, I could tell this really hurt him and he wanted me to try more, try longer for the feelings to set in. To me, that would have just prolonged the inevitable and made things more uncomfortable. I preferred to be true and honest vs crafting a narrative. So, just after 2 short weeks, I ended our experiment. He didn't take it well. We still played sports together but I could tell things were really off. He seemed very let down and like a light had drained from him. I went away on a trip for a month and a half shortly after and he said he would prefer if we didn't talk during that time. We had a long convo when I got back and he mostly seemed bummed that I didn't try harder or longer, despite me knowing that wouldn't have helped.

We agreed to get back to being friends, but over the coming months, he has been even more distant, very standoffish, even blatantly ignoring me at times. I haven't seen him smile or laugh ONCE since January. It has caused uneasy feelings with our sports team and friend groups too. I reached out telling him that the standoffishness and stonewalling has been hurting my feelings and that I miss our friendship. He responded by saying he needs to distance himself from me so he feels "safe", and he removed himself from our sports team we founded a few years ago. It has been 5 months since all of this started and only a few days since he said he doesn't want to talk to me at all. I'm really at a loss. I've always created a safe environment for him to tell me anything, and I've always felt the same in return. I can't help but feeling like I've done something wrong, but I know in my heart, that I didn't...I just simply couldn't return the strong feelings he was having. I've thought this person would be in my life for a long time, now I don't know if we'll ever be able to have a friendship again. I have a feeling he is on a shame/rejection spiral and it seems really intense. I want to give him his space and respect his boundary to feel safe. I also want him to know that I respect him and love him and that I will be his friend no matter what. I want to send him a letter that he can open when he feels comfortable, just letting him know I'm there for him. Will that hurt the situation? Or will it be helpful for him to know he's not truly alone? I'm feeling really alone in this and it's hard to speak with our mutual friends about it because I don't want them to feel caught in the middle. Anyone ever experience this? What's your advice??