Sure, their UX is more polished, and due to using residential IPs they aren't so easily blocked out. But there is a different reason for the popularity: NordV

Sure, their UX is more polished, and due to using residential IPs they aren't so easily blocked out. But there is a different reason for the popularity: NordVPN and others spend a lot of money on aggresive and pretty shady advertising, which tricks consumers into all kinds of false assumptions.