I mean, two things can be simultaneously true: The Rangers are a very good team, and they have also been lucky.
They've played some legitimately good hockey. They play a style that maximizes their strengths (creating quality chances) and leverages their big advantages over other teams (special teams and goaltending). They have a formula that works. They walked over WAS, as expected, played Carolina very well, and have played Florida tight too (with the exception of game 3).
That said, they've won most of these one-goal or OT games, where one errant bounce is the difference between winning and losing. Obviously, you're getting some degree of luck if you're always winning the 50/50 coin flip games.