If the monsters saw the spell casted and saw the Ranger climb up the rope, then yes, it makes sense that the monsters would follow in kind. If they didn't see the spell casted before the encounter then it should have stumped them and the monsters, depending on their intelligence/leadership, shouldn't have been able to figure it out. Even then it would be a roll with Disadvantage for the monsters to attempt to "resolve' the issue at that point.
And then it's entirely possible that the entire act of "seeing the rope" and just standing there, tugging at it, while the party all sneak around the back behind them to safety, also makes logical sense.