Why would a guy escalate intimacy/sex so much and then suddenly say he can’t do casual?

I (27F) met a guy (let’s call him S, early 30s) recently and I’m really confused by how quickly things changed. I’m not looking for a relationship with him necessarily — I was genuinely enjoying what we had and was happy to let it be casual.

Context: He is leaving the country in around 7 months because his visa is expiring. He’s actually quite sad about leaving because he’s built a life here, so I think that may also be relevant to his headspace.

From fairly early on, he told me that casual sex doesn’t really work for him unless he feels extremely comfortable with someone first. He wanted to spend time together and get comfortable rather than just jump straight into sex. I was actually happy to keep things fun and sexual from the beginning 😂, but I went along with his pace because I liked him and respected what he said he needed. And he seemed to actively want the closeness himself.

He would hold me, pull me closer while we were literally just talking caressing me kiss my head my face tickle me play with my hair squeeze me etc. and On our third date he kissed my head/forehead constantly without me asking. We spent a lot of time physically close and making out. He seemed very affectionate. Even post dates lots of enthusiastic affectionate cute texts from him seemed very much into me.

At the same time, the sexual escalation was getting stronger and stronger. he week leading up to the third date was probably the most sexually enthusiastic he’d been. He was texting me during work about how much he couldn’t wait to touch me, telling me I was irresistible, etc. He had also recently asked to see me naked/shared intimate pictures with me.

On the third date, the intimacy got particularly intense. At one point I was sitting on his lap and he made it very clear he didn’t want me getting off. Even when we stood up, he continued kissing me. He was very physically affectionate throughout.
Then the day after, his first message was basically that he was still thinking about me on his lap and how good it would feel to have sex with me.
So I was thinking: okay, we’re getting closer, he’s clearly very attracted to me, we’re becoming more comfortable, and this is progressing naturally.
But then he started saying he doesn’t know if he can actually do casual he felt unsettled/ not great after the third date?? Very confused.

That’s the bit I can’t understand. I wasn’t asking him for a relationship or commitment. I was genuinely enjoying what we had. If the emotional closeness was making it feel less casual to him, I would’ve been completely capable of saying, okay, let’s keep it purely physical and take the holding/kissing/spending-time-together-outside-of-sex stuff out of it. Instead, he seems to have pulled away.
I’m confused because he was the one who wanted a lot of the closeness in the first place, and his sexual enthusiasm was actually increasing immediately before this happened.

What I’m trying to understand is:
Why would someone actively seek this much physical/sexual closeness if they’re ultimately uncomfortable with casual and I never asked for more?