I never even noticed until the news reported on it.
I don't know if it was purposely done to show disrespect because I don't know Zelenskyy's character. Does he wear suits at all? Has he worn a suit in the past? Okay, just searched and he did not wear a suit when he spoke with Biden. So, no need to get mad about it.
I don't think I have seen him on a suit since the start of this war. Refusing to wear a suit publicly is in solidarity with the Ukrainian soldiers giving their all in the field to protect the country.
It's pretty obvious this was a bullying session against Zelensky. I've been there before. You meet with family or whatever and there's all this passive aggression.