Based on the livestream of the incident, I personally think the issue was the lack of a Ukrainian-English translator.
Vance was absolutely trying to score domestic political points by undermining Zelenskyy, but Zelenskyy was unable to communicate or respond in the manner he wanted to, and definetly committed some obvious Russian L1 / English L2 mistakes (Zelenskyy's first language is Russian and this can be seen by his "costume" statement, because the direct translation for suit across the CIS is костюм/costume [0][1][2][3] because of French influence), and he inadvertently insinuated that Trump wasn't doing enough even though he was trying to join Vance in dunking on the previous admin.
This is why the Japan and India meetings with Trump had English translators despite Ishiba and Modi having a similar level of English fluency to Zelenskyy.
Vance was absolutely trying to score domestic political points by undermining Zelenskyy, but Zelenskyy was unable to communicate or respond in the manner he wanted to, and definetly committed some obvious Russian L1 / English L2 mistakes (Zelenskyy's first language is Russian and this can be seen by his "costume" statement, because the direct translation for suit across the CIS is костюм/costume [0][1][2][3] because of French influence), and he inadvertently insinuated that Trump wasn't doing enough even though he was trying to join Vance in dunking on the previous admin.
This is why the Japan and India meetings with Trump had English translators despite Ishiba and Modi having a similar level of English fluency to Zelenskyy.
[0] - https://stager.ua/ru/category/kostyumi/
[1] - https://arber.ua/ru/catalog/kostiumi
[2] - https://online.voronin.ua/ru/katalog/kostumy/
[3] - https://en.m.wiktionary.org/wiki/костюм