Vocal melody is only the root note of each chord throughout both the verse and the chorus. The phrase modulation from the dissonant progression rooted in A minor (verse) to the hardcore-like progression rooted in F# major (chorus) is a real example of a writer just reaching for anything at all, regardless of tonal relationships. Works because of the surprise, the aforementioned melodic simplicity, and the energy with which Spizz as vocalist nails it.
The idea of this chorus is so good, in fact, that Spizz just repeats the first two lines over again. And then this four-line structure, the whole of the chorus, is such a good idea in itself that they repeat it after each verse.
Topping things off, this 4:38 track could easily end with the vamp on the verse chord progression after the third chorus, but instead includes a coda of entirely new musical materials in another somewhat random key (B major). Suggesting even more of a sense of urgency, Spizz reduces the melody on this final section to one note only.