Why did he stop pursuing me suddenly?

I met this guy through work and there were vibes right away, he asked for my number that same day and texted me every few days for the next couple weeks. He also asked me about my relationship status the first day, and I had been very upfront and told him that I was single but I still talked to my ex a lot. Clearly it didn't bother him since he still kept in touch with me so frequently, and he even asked me on a coffee date two days after we first met. Then about a week and a half ago I visited him while he was at work and during our conversation I told him that my ex was planning to visit me the following weekend. He didn't seem upset and told me if he ended up not coming to let him know and invited me to his plans for that weekend. He hugged me goodbye and texted me afterwards and everything seemed normal. But then that was it. The following week he didn't text me at all, which was the longest we'd ever gone without speaking. I thought it was a little odd but figured he just wanted to stay out of the way since my ex was coming.

Well, my ex ended up NOT coming, and I decided to text the work guy and just see if he was still going to the plans he invited me to. Compared to all our past conversations, this one was very short and dry. He was very faintly flirtatious but not like normal, and then the conversation ended and its now been another 4-5 days that we have gone without speaking, so I think its safe to say the energy has changed. Oh, and we didn't end up hanging out.

Do you guys think he is just butthurt about my ex-situationship? I understand if he is, I just think its weird considering he knew from the start that my ex was still in the picture. The only thing I can think is that he dwelled on it more and it started to bother him or maybe he thought because we had been talking so much that I would cut my ex off. But none of our conversations had been directly about dating each other, just flirty. If he had legitimately asked me out then maybe I would have.

Why did he stop pursuing me suddenly?
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