Why isn't a class being added to a loaded nav element?

this.loadTemplate = async(currentPage) => {
  let promise = new Promise((resolve) => {
    $(() => $("#nav").load("./nav.html"));
    $(() => $("#footer").load("./footer.html"));
    resolve("resolved");
  });

  let result = await promise;
  console.log(result);
  $(`#${currentPage}`).addClass("current-page");
};

Above is the code for loading and adding the class to the nav.html file. Which should change an element to orange. Which it doesn't.

Any help is appreciated.