It cannot be a just a fluke. They sold their most known assets (bar Osimhen) and brought two mostly unknown players (Kim and Kvara) that rocked the league INSTANTLY. Yeah, ADL is a horrible president, he meddles too much, letting go of Giuntoli (who probably left because he knew Napoli is a sinking ship) ... Without Giuntoli this Napoli is the same as Inter before Marotta. Just wasted potential.
Sure it was unexpected, but I wouldn't say they won by luck, it was a project that started before Osimhen was brought, while other rival teams were making stupid moves (Lukaku, Pogba, Milan spending money on the wrong young players)