Why did he come back?

We met on a trip in Berlin and we were talking about anything and everything, so it smoothly went to sex talks and him talking about moving to my country and making an effort to be together. We live in different countries, on different continents.
All those talks were initiated by him, not that I didn't like it, but I was aware these things are not a fairytale and they dont happen just like that. So, one day he blocked me everywhere not mentioning anything. A month after, I reached out to him and he said that it became impossible for him to move especially after he had 2 failed attempts, and that he made a mistake and regret it. What he also said is that he would like to make an effort to rebuild the relationship with me. It was something I didn't expect, because I expected to hear that he just stopped liking me or just that thing became too complicated, which would be bad to hear but it is life. Rebuilding the relationship surprised me and kind of scared me cause I know it won't be easy.

However, we talked 5 days ago and he haven't spoken to me since.

i say "next".
typically when they disappear so suddenly and without explanation - it's because they are with somebody else or met somebody else and decided to be with them. that is why the month break.
his explanation for why he BLOCKED you though (and simply besides ignoring you) - does not wash. i've got to believe the blocking is so your messages can't come thru where somebody else might see it and et him into trouble.

he tried 2X to move to your country even though you were not in contact? this does not make any sense either no?

you are right to wonder. be scared. i would not rebuild anything with him if i were you.