Why did he invite me to his brother's wedding but was surprised when I showed up?

Anonymous
I haven't met my guy friend in a year because he was in a different timezone.
So when he invited a few mutual friends and me, I said that I would attend. However, when I showed up he looked stunned and while he was polite to me, he seemed to sort of keep away until the evening ended where he apologized because I was alone and didn't know anyone there.
Considering it was after a long time, he sort of looked intense and didn't speak as old friends should.
Did I do something wrong?
Why did he invite me to his brother's wedding but was surprised when I showed up?
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