When Zelenski was criticized by a reporter during the meeting with Trump for not wearing a suit, his comeback was that he'll go back to wearing suits ("costumes" though I hear that may have been a mistranslation on his part) when the war is over. The reporter was trying to frame his attire as disrespectful to the President, Zelenski's response made it clear that he'd have found wearing a suit disrespectful to his people who don't have the luxury of returning to civil life until the war ends. Make of that what you will but it signalled confidence and empathy. It came off as authentic. Trying to compensate his height with footwear would have had the opposite effect and conflicted with this.

DeSantis on the other hand tried to appear "tough" and decisive but was ridiculed for his footwear because it was so obvious and so exaggerated that it made him appear extremely insecure about his height. But I think it would have looked even worse if he had been in Zelenski's position (and wearing a uniform) because of this contradiction.