The drag ropes were causal, but in a complicated way. They did not - and could not - function as intended, which was as a means of flying in a direction significantly different from that in which the wind was taking them, allowing them to navigate towards a specific destination.

Without this assumption, it seems unlikely that they would have attempted to do what the flight actually was: a drift in a free balloon over the arctic. After several days, the balloon came down onto the ice (it did not "plummet") as a result of losing gas gradually, with ice accumulation probably being a factor.

I have seen a report of the press conference they gave before starting, and it seems painfully clear that they would have all abandoned the attempt if any one of them would have said, out loud, that it was a bad idea.

He lost two of the three during launch, and even if he had kept them, there's no evidence they had any steering effect, and no reason to believe they could have had any. That is, their contribution to the failure of the expedition was increased overconfidence.