While Trump remains the frontrunner in the GOP race for the White House, he has also been indicted in four criminal cases this year, and therefore cannot purchase a gun under the law.
A federal judge in texas ruled last year that preventing people under indictment from purchasing firearms was unconstitutional based on the Supreme Court's Bruen decision, just FYI. So I don't think the situation is as cut and dry as it would have been just a couple years ago.
I don't really think it's super worthwhile to spend a bunch of time discussing if and should about those cases here. The larger point is that he apparently tried to lie about his gun cred by pretending to buy a gun. And that of he had, he would have been committing the same crime they got Hunter with.