But who needs a "Hakuna Matata" retread when you already have a "Let It Go"?? ;-)
Also - Hakuna came from the animated film, so it already had a huge recognition factor.
And - had they really wanted a big hit, they might have written a slightly less complex melody. I'm not sure "Hygge" would ever be considered as immediately catchy as, say, the equally quirky/bouncy "Roll In The Hay." (And probably neither song really belongs in a show geared to very young audiences, lol.)