Why he blocked me out of blue?

Me and this guy made it clear from the start that we are only interested in casual hook up. He was usually the one initiating the contact and only texted me in a case when he wanted a sex. My schedule is usually full and he didn’t make plans with much time ahead, so it often happened, that I didn’t have a time when he suggested a meeting. Today, he texted me if I am free today. I am not and explained him why. He tried to convince me. But I for real wasn’t able to make it. He responded with “ok”, then blocked me. I am not blocked on whatsapp tho. Why do you think he blocked me? I wasn’t bothering him, I always politely explained why I don’t have time. Sometimes, he doesn’t have a time too, when I suggested something and even cancel our meeting twice.
Why he blocked me out of blue?
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