I can only speculate and guess, but I think the main issue is the fact that he knew you were just visiting. It's fun when you're together, but is a long distance different country relationship with someone you just met really worth it? Could he convince you to move? Could he move? The long term prospects just might not be there.

It's also hard to socialize one on one just over the internet. Maybe he builds on the energy your physical presence brings, but when it's gone, there isn't enough to keep that engine running with everything else going on.