Well, I don’t have a study backing me up, but in my experience, promising what you can’t deliver often results in being called a liar.
I really don’t know why “other candidates do it” would be an excuse. The whole pitch for voting for him is that he is supposed to be better than the other candidates. Seems like whataboutism.
I get what you’re saying on principle, but the reality is that the world does not work like that. There’s a reason populism is often a quick way to get to power, because you just promise whatever people want to hear so you could be elected. People don’t vote based on logic, people vote based on emotion, which means people don’t consider what is realistic, they consider what speaks to them.